The BSA A7-A10 Forum

Technical => Frame => Topic started by: Scott and Jay on 21.01. 2021 05:22

Title: Tire pressures for "Classic" spec tires
Post by: Scott and Jay on 21.01. 2021 05:22
Hi all, I searched the topic in this forum, first. It seems the recommendations about high 20s, front, and low 30s, rear - have been for "modern" spec tires - Avon Speedmasters? I have just been getting Dunlop K70 "replicas". They only cost NZ$175. On the invoice they are called "K70 Classic". I came off my A10 on the 21st November, caught out by a sudden side-gust. Our club repairer is great, he's basically come out of retirement for my insurance job. He said I had been way over-inflating. I said that' what the forums are recommending now for "modern" tires. But he said mine were basically old-spec. It was verified by the wear-pattern. He said it would make it "skittery" which it did seem to be
So, is it that these "classic" tires aren't really modern just because they have been recently manufactured. They still have the "thick walls" like original NOS Dunlops. There are Mitas (Czech) tires on Jay's new A65 acquisition. They were only inflated low by the PO. Looking them up online - they are also called "classic". I have put them (up) to 19 front, 22 rear. I think I will now run my A10 at 21 front, 24 rear. Any comments, thanks..
Title: Re: Tire pressures for "Classic" spec tires
Post by: muskrat on 21.01. 2021 07:53
G'day S&J.
I've got new TT100's on the plunger with 30 & 32 and find them great but the plunger don't lean like the Cafe with Roadriders at 34 & 36.
At the end of the day it's what your comfortable with for your riding style. Getting it right for you can be scary with the thought of sliding down the road in your mind *eek*
Myself I wouldn' go as low as your planing.
As a side I had a good conversation with a mate about Harley tyres. He uses max pressure of 40/42  *eek*. I know if I did I'd be off in the first corner on mine. 32/34 is good for me.
Cheers
Title: Re: Tire pressures for "Classic" spec tires
Post by: Triton Thrasher on 21.01. 2021 08:38
Your club repairer, like everyone else, has opinions.

Title: Re: Tire pressures for "Classic" spec tires
Post by: KiwiGF on 21.01. 2021 09:05
Yo scott, when i ran dunlop k70’s, not sure if they are the same as your “classic” k70’s, I initially used the book figures, of the period, of around 20psi, then after getting less than 3000 miles out of a rear tyre 🤬  I was advised to use nearer 30psi. This made no difference to tread wear unfortunately 🤬🤬🤬 but seemed a bit safer around corners etc.

I now avoid dunlop tyres due to the incredibly rubbish tread wear, and use “duro” brand tyres, which start with 5/16” deep tread versus the 1/4” of the dunlops, and whilst I have not worn one out yet, these look good (on the rear) for over 6000 miles. I am not a good enough rider to tell if the better wearing compound of the duro tyres results in less grip. I have not worn a front k70 tyre out yet....

I expect to get 12,000 miles from the tyres in my gold wing, which has 115hp and weighs 410kg, go figure. The goldwings tyres (avons) are twice the price of the skinny duros though. It seems the tyre makers (for modern bikes) want you you to replace both tyres at once and the front tyres start with a lot less tread than the rears.
https://www.a7a10.net/forum/index.php?topic=11470.0

Edit: another factor to consider is how the tyre wears and how long one spends with a tyre that has (despite best efforts around corners) worn flat, as that leads to weird handling...for me thats another reason to avoid k70’s as after 2000 miles they have lost their profile and are flat, as you eke thevlast expensive 500 miles or so out of them.
Title: Re: Tire pressures for "Classic" spec tires
Post by: Butch (cb) on 21.01. 2021 09:17
I think tyre pressures in days of yore were much less, and I presume due to a stiffer construction and materials back then. Unless these 'classics' are somehow similarly produced then I'd presume they need higher pressures. I'm neither a good or speedy rider and regardless of what I'm on I go with around a low 30 at the front and a mid 30 at the back.
Title: Re: Tire pressures for "Classic" spec tires
Post by: groily on 21.01. 2021 09:45
Under 3K miles from a TT100 on my A too, now trying a Road Rider at the back with TT100 still up front. K70 rear on a Dommie did even worse - truth in that comment about Dunlops. 
Avon SMs gave me 6K+ comfortably on the rear. Others I've tried include Road Runners some years ago on various machines, and Metzlers and  Pirelli Scorpion (18 incher) on my desert sled. Can't think I've whined about any of them like I have about Dunlops - but nor can I deny that TT100s do handle quite nicely.
Around 30psi for me.
My only 'modern', an XJR Yam which is 21 this year, tends to go 'square' on recommended pressures before all the tread wears off on the rear. About 6K miles on them I think. Massive darn thing, with price to match - using Pirelli Angels at the moment on that, and like them well so far.
Title: Re: Tire pressures for "Classic" spec tires
Post by: Rex on 21.01. 2021 10:05
19 front and 22 rear would be dangerously low to me and you must be wallowing all over the road on those pressures.
 I go for 28 front and 30 rear.
Title: Re: Tire pressures for "Classic" spec tires
Post by: Black Sheep on 21.01. 2021 10:43
I go for about 22 /25. Works for me.
Title: Re: Tire pressures for "Classic" spec tires
Post by: bsa-bill on 21.01. 2021 11:27
Quote
I go for 28 front and 30 rear.

I'm with Rex, when I restored my Flash (2000) I set the pressure as BSA spec and didn't like the ride at all, then I read somewhere (possible here) that new versions of the tyres we used back in the day are made differently so while the tread pattern may be the same the carcass construction is not and requires higher pressure
Title: Re: Tire pressures for "Classic" spec tires
Post by: RoyC on 21.01. 2021 11:59
I put 35psi front and rear, sidecar fitted.
Don't want the tyres slipping round on the rim when accelerating/braking.
Title: Re: Tire pressures for "Classic" spec tires
Post by: JulianS on 21.01. 2021 13:19
This from Avon Tyres;

https://www.avontyres.com/en-gb/tyre-care/motorcycle-tyres/

You can see what they say about classic bikes.
Title: Re: Tire pressures for "Classic" spec tires
Post by: Black Sheep on 21.01. 2021 15:04
Elaborating a bit. Using 30+ psi certainly makes the bikes skittery, especially in the wet, probably because of the reduced contact patch. The same contact patch reduction accelerates wear on the centre of the tread - especially noticable on TT100s, which in my experience were great for racing but I wouldn't use on the road. All that tread reaching up to the sidewalls that you can never use. I find for both plunger and S/A BSAs that the old fashioned looking but modern rubber Avon Speedmaster / SM MkII combination is as good as any.
The Star Twin is currently on trials tyres and the roadholding is still good - you can touch down the centre stand on the left and footrest on the right but the handling is rather interesting.   
Title: Re: Tire pressures for "Classic" spec tires
Post by: RDfella on 21.01. 2021 15:17
Well, the tyre manufacturers can specify what they like. I have several classics and most wear speedmaster on the front, K70 on the rear. Lately I've been moving to Avon roadrunner universal on the rear. On most bikes I run around 20psi front and rear (slightly less on rigids for the rear). Tried this 30psi nonsense and it's dangerous. The tyre compound may have changed, but no appreciable change in the construction (walls etc) and nor should there be. Bit like when radial tyres came out - some cars, designed around crossply tyres, were positively dangerous when shod with radials. My (modern) Honda runs 36 / 42 but that's radials on completely different platform.
Title: Re: Tire pressures for "Classic" spec tires
Post by: berger on 21.01. 2021 16:29
being a slimish dwarf at 5ft 8inch and 11stone I run 20  front 24 rear solo and  24 front 30 rear with passenger , with French made TT100's. most times I forget to drop the pressure when riding solo again and can tell the difference when hitting uneven road on corners it gets a bit skippy. the mention of these wearing in the middle and expense of replacements would bother me if I was doing 3000 miles a year but I don't, BUT I have seen good reports on some other tyres on this forum and might venture to another make this summer.
Title: Re: Tire pressures for "Classic" spec tires
Post by: Triton Thrasher on 21.01. 2021 16:44
I get good results using manufacturers’ recent recommendations.
Title: Re: Tire pressures for "Classic" spec tires
Post by: Black Sheep on 21.01. 2021 18:38
One other consideration if using 30+ psi is that these pressures are fine for modern bikes with radial tyres and supple suspension. Our bikes don't have supple suspension (who would have guessed) and rely on a bit of tyre deformation to give decent roadholding. With high pressures, there isn't that give which is why they become skittish on corners.   
Title: Re: Tire pressures for "Classic" spec tires
Post by: BSA_54A10 on 22.01. 2021 08:28
Hi all, I searched the topic in this forum, first. It seems the recommendations about high 20s, front, and low 30s, rear - have been for "modern" spec tires - Avon Speedmasters? I have just been getting Dunlop K70 "replicas". They only cost NZ$175. On the invoice they are called "K70 Classic". I came off my A10 on the 21st November, caught out by a sudden side-gust. Our club repairer is great, he's basically come out of retirement for my insurance job. He said I had been way over-inflating. I said that' what the forums are recommending now for "modern" tires. But he said mine were basically old-spec. It was verified by the wear-pattern. He said it would make it "skittery" which it did seem to be
So, is it that these "classic" tires aren't really modern just because they have been recently manufactured. They still have the "thick walls" like original NOS Dunlops. There are Mitas (Czech) tires on Jay's new A65 acquisition. They were only inflated low by the PO. Looking them up online - they are also called "classic". I have put them (up) to 19 front, 22 rear. I think I will now run my A10 at 21 front, 24 rear. Any comments, thanks..

You inflate the tyre to the makers specification .
Modern tyres run harder than the tyres fitted when the bike was new.
From there you buy a tyre gauge from a push bike shop because they have a smaller range and tend to be more accurate.
From there you start adjusting the pressure in 2 psi increments till they ar comfortable for you.
Adjust them one at time
Remember that if you do it is a single day, the tyres will be getting hotter & the pressure will be increasing .
When you fell you have them right go home & in the morning measure the pressure again.
That is your COLD pressure  .
If you ride like Musky then keep the gauge in your riding kit because servo gauges are rarely accurate.
Title: Re: Tire pressures for "Classic" spec tires
Post by: KiwiGF on 22.01. 2021 11:02
Info from dunlop is hard to find on the net, not surprising I suppose given the age of our bikes if they are not “supported” by dunlop.

However, dunlop do “support” modern 500cc single royal enfields, which are pretty similar to our bikes in terms of weight and horse power, and tyre size. They are included on their application documents, and recommend 5he k70 as an approved fitment, with front 24psi, rear 32psi. See pic attached.

To some extent I think this adds weight to the opinion that the newer k70 tyres need to have higher pressures than those made in the 50’s and 60’s.

Just my 2 cents worth.

Title: Re: Tire pressures for "Classic" spec tires
Post by: RogerSB on 22.01. 2021 17:14
Ha! We've been here before.

I queried K70 pressures with Dunlop in 2018. Here are two of the replies received (note: recommended pressures given in 2nd email).

Mine are K70 Gold Seals and are ok 2 years on and during all of 2020 with a sidecar attached.

Title: Re: Tire pressures for "Classic" spec tires
Post by: Flashgreubon on 22.01. 2021 19:47
Hi to all,
I posted a while ago a method to ascertain the correct tyre pressure for your bike, taking in consideration your load and the road temperature.
This applies to all types of tyres and is worth doing if you are in any doubt : it puts to bed any speculations on the subject

https://www.a7a10.net/forum/index.php?topic=13269.msg106923#msg106923
Title: Re: Tire pressures for "Classic" spec tires
Post by: Scott and Jay on 24.01. 2021 01:21
Thanks very much for all the replies. I can weigh up all the contrasting input and come up with a plan..
Title: Re: Tire pressures for "Classic" spec tires
Post by: Butch (cb) on 25.01. 2021 10:40
This dialogue had me wondering how accurate the gauge might be on my old Halfords foot pump. Checking with one of those admittedly somewhat crude blow out rod testers suggests the foot pump is over reading by about 5-7 psi. Maybe I need to get a better gauge so as to be sure. 
Title: Re: Tire pressures for "Classic" spec tires
Post by: Greybeard on 25.01. 2021 11:06
I'd like to get a good quality inflator for my compressor. Can you recommend one for me?
Title: Re: Tire pressures for "Classic" spec tires
Post by: RoyC on 25.01. 2021 11:38
I'd like to get a good quality inflator for my compressor. Can you recommend one for me?


I have one like the ones that they use on garage forecourts and the reading is bang on.

It's no good for the BSA though, can't get it on the tire valve.
I use a foot bump and a tire gauge for them.
Title: Re: Tire pressures for "Classic" spec tires
Post by: Greybeard on 25.01. 2021 16:13
I'd like to get a good quality inflator for my compressor. Can you recommend one for me?


I have one like the ones that they use on garage forecourts and the reading is bang on.

It's no good for the BSA though, can't get it on the tire valve.
I use a foot bump and a tire gauge for them.
Why can't the dooberry fit on the wossname? Is it the brake drum that's the problem? What about putting a bend in the metal tube; would that help?

I was looking at a tyre guage like that. They are quite expensive.
https://www.amazon.co.uk/dp/B000RO3P8I/ref=cm_sw_r_cp_apa_i_s8UdGbQRJ8YJZ
If they are no good for the BSA I'm glad you told me. Thanks!

What kind of tyre guage do you use?
Title: Re: Tire pressures for "Classic" spec tires
Post by: Butch (cb) on 25.01. 2021 16:29

I have one like the ones that they use on garage forecourts and the reading is bang on.

It's no good for the BSA though, can't get it on the tire valve.
I use a foot bump and a tire gauge for them.

https://www.ebay.co.uk/itm/90-Degree-Angle-Tyre-Valve-Extension-Adaptor-Motorcycle-Motorbike-Car-Bike/113766791704?hash=item1a7d077a18:g:ihMAAOSwUn9aAX5d
Title: Re: Tire pressures for "Classic" spec tires
Post by: RoyC on 25.01. 2021 17:09

I have one like the ones that they use on garage forecourts and the reading is bang on.

It's no good for the BSA though, can't get it on the tire valve.
I use a foot bump and a tire gauge for them.

https://www.ebay.co.uk/itm/90-Degree-Angle-Tyre-Valve-Extension-Adaptor-Motorcycle-Motorbike-Car-Bike/113766791704?hash=item1a7d077a18:g:ihMAAOSwUn9aAX5d


I have got four of those extensions, they are no good, they all leak giving you a slow puncture, unless you remove them after inflating the tire but you will have to over inflate to compensate for the air loss while removing it.
Title: Re: Tire pressures for "Classic" spec tires
Post by: RoyC on 25.01. 2021 17:18
What kind of tyre guage do you use?


I use one of these.
https://www.ebay.co.uk/itm/PROFESSIONAL-TYRE-PRESSURE-GAUGE-AIR-MEASUREMENT-PSI-BAR-RELEASE-BUTTON-CAR-BIKE/333662594264?hash=item4dafd724d8:g:q18AAOSwlFxfGuq4   
Title: Re: Tire pressures for "Classic" spec tires
Post by: RoyC on 25.01. 2021 17:39
I was looking at a tyre guage like that. They are quite expensive.
https://www.amazon.co.uk/dp/B000RO3P8I/ref=cm_sw_r_cp_apa_i_s8UdGbQRJ8YJZ
If they are no good for the BSA I'm glad you told me. Thanks!


They are less expensive on ebay.

https://www.ebay.co.uk/itm/Clarke-Linear-Tyre-Inflator-Push-On-Connector-Garage-Forecourt-Workshop/324373068007?_trkparms=aid%3D111001%26algo%3DREC.SEED%26ao%3D1%26asc%3D20160727114228%26meid%3Da853ad1f8f2446d3b23dd30e52f78e24%26pid%3D100290%26rk%3D1%26rkt%3D4%26sd%3D324373068007%26itm%3D324373068007%26pmt%3D1%26noa%3D1%26pg%3D2060778%26brand%3DClarke&_trksid=p2060778.c100290.m3507   


Only £28 here   -   https://www.ebay.co.uk/itm/New-Professional-Garage-Air-Line-Gauge-Inflator-Inflater-Pump-And-Pressure-Tyre/123873172395?_trkparms=aid%3D1110006%26algo%3DHOMESPLICE.SIM%26ao%3D1%26asc%3D20200520130048%26meid%3De71cb96284cd499a8386377861c3d4a2%26pid%3D100005%26rk%3D6%26rkt%3D12%26mehot%3Dlo%26sd%3D324373068007%26itm%3D123873172395%26pmt%3D1%26noa%3D0%26pg%3D2047675%26algv%3DSimplAMLv5PairwiseWebWithDarwoV3BBEV2b%26brand%3DUnbranded&_trksid=p2047675.c100005.m1851
Title: Re: Tire pressures for "Classic" spec tires
Post by: muskrat on 25.01. 2021 20:17
G'day Fellas.
I use one like this https://tinyurl.com/y4elguon
Then I double check pressure with a digital.
Cheers
Title: Re: Tire pressures for "Classic" spec tires
Post by: Butch (cb) on 26.01. 2021 08:29

https://www.ebay.co.uk/itm/90-Degree-Angle-Tyre-Valve-Extension-Adaptor-Motorcycle-Motorbike-Car-Bike/113766791704?hash=item1a7d077a18:g:ihMAAOSwUn9aAX5d

I have got four of those extensions, they are no good, they all leak giving you a slow puncture, unless you remove them after inflating the tire but you will have to over inflate to compensate for the air loss while removing it.

Yeah, I don't leave them on, and I guess they'd mess with wheel balance if you're sensitive to such things. I figure I don't lose any more pressure taking them off than when I remove a pump nozzle.
Title: Re: Tire pressures for "Classic" spec tires
Post by: Jules on 26.01. 2021 09:36
I still use the good old standard tube in tube, sliding out gismo, have done for years without fault....I guess the issue is which device is correct when checking one to another, so I use the pump gauge initially to get the air in, then my trusty gauge to set them, for consistency  at least.....
Title: Re: Tire pressures for "Classic" spec tires
Post by: Greybeard on 26.01. 2021 09:52
My dad had one of those tube-in-tube pocket pressure guages. Are they accurate?
Title: Re: Tire pressures for "Classic" spec tires
Post by: RoyC on 26.01. 2021 11:14
My dad had one of those tube-in-tube pocket pressure guages. Are they accurate?

I've got a couple of those, had them for years.
I haven't got a clue where they came from.
Title: Re: Tire pressures for "Classic" spec tires
Post by: Triton Thrasher on 26.01. 2021 11:30
My dad had one of those tube-in-tube pocket pressure guages. Are they accurate?
(https://i.ebayimg.com/images/g/8wsAAOSwQItUI~Fe/s-l300.jpg)

You can call me “Two-Schraders!”

They are typically accurate enough.  Tests done by a motor magazine in the 1970s showed the old type to be more accurate than small dial-type gauges and much more accurate than many garage forecourt ones.

Stick to one gauge of your own and you’ll get consistent results, even with the inaccuracies.
Title: Re: Tire pressures for "Classic" spec tires
Post by: muskrat on 26.01. 2021 18:50
Stick to one gauge of your own and you’ll get consistent results, even with the inaccuracies.
I agree 100%. Pump the tyres up with the inflator to a few Lbs over then adjust with your gauge. Using the same gauge all the time and you know where you stand. I prefer the digital ones for accuracy.
Cheers
Title: Re: Tire pressures for "Classic" spec tires
Post by: BSA_54A10 on 27.01. 2021 09:50
My dad had one of those tube-in-tube pocket pressure guages. Are they accurate?

Does not matter.
All that is important is if 9 on the gauge is right for you then you inflate them above that then bleed down to 9 .

I have a dozen different tyre gauges and it would be very rare for them all to read the same
Rule of thumb, to smaller the full scale range the more accurate the reading should be
Thus I have two 0-20 psi gauges for mowers
Three 0-40 psi gauges for cars & motorcycles
two 0-60 psi for trucks
Title: Re: Tire pressures for "Classic" spec tires
Post by: Greybeard on 27.01. 2021 10:15
I'd like to get a good quality inflator for my compressor. Can you recommend one for me?


I have one like the ones that they use on garage forecourts and the reading is bang on.

It's no good for the BSA though, can't get it on the tire valve.
I use a foot bump and a tire gauge for them.

You didn't explain so I'm asking again:
Why can't the dooberry fit on the wossname? Is it the brake drum that's the problem? What about putting a bend in the metal tube; would that help?
Title: Re: Tire pressures for "Classic" spec tires
Post by: RoyC on 27.01. 2021 10:45
I'd like to get a good quality inflator for my compressor. Can you recommend one for me?


I have one like the ones that they use on garage forecourts and the reading is bang on.

It's no good for the BSA though, can't get it on the tire valve.
I use a foot bump and a tire gauge for them.

You didn't explain so I'm asking again:
Why can't the dooberry fit on the wossname? Is it the brake drum that's the problem? What about putting a bend in the metal tube; would that help?


Sorry GB.
On my inflator I have to pull a fitting back to lock it onto the valve.
From memory, there isn't enough room to get my fingers between the spokes to do this.
No problem on the car.
It only takes a couple of dozen pumps with the foot pump so no problem.
Title: Re: Tire pressures for "Classic" spec tires
Post by: Greybeard on 27.01. 2021 12:53
Why can't the dooberry fit on the wossname? Is it the brake drum that's the problem? What about putting a bend in the metal tube; would that help?

Quote

On my inflator I have to pull a fitting back to lock it onto the valve.
From memory, there isn't enough room to get my fingers between the spokes to do this.
No problem on the car.
It only takes a couple of dozen pumps with the foot pump so no problem.
Ah, I understand. Cheers m'dear.
Title: Re: Tire pressures for "Classic" spec tires
Post by: Rex on 27.01. 2021 13:10
I ordered a small connector of the type mentioned above, ie a small lever is pulled back which then locks it onto the valve stem. It came from China (surprise surprise) but it's actually a surprisingly well-made item.
Doesn't have an in-built gauge so I check it with an ancient Duco sliding gauge which came from my dad's workshop decades ago, which reads pretty much the same as both the footpump gauge and the workshop compressor trigger inflator.
Title: Re: Tire pressures for "Classic" spec tires
Post by: RoyC on 27.01. 2021 14:05
Why can't the dooberry fit on the wossname? Is it the brake drum that's the problem? What about putting a bend in the metal tube; would that help?

Quote

On my inflator I have to pull a fitting back to lock it onto the valve.
From memory, there isn't enough room to get my fingers between the spokes to do this.
No problem on the car.
It only takes a couple of dozen pumps with the foot pump so no problem.
Ah, I understand. Cheers m'dear.

Just been down the garage to have a look why I couldn't use it on the bike.

A.  It's not offset.
B.  Awkward to operate the locking trigger.

Title: Re: Tire pressures for "Classic" spec tires
Post by: Greybeard on 27.01. 2021 17:28
Maybe one of those guages but with a rigid tube would be OK.
Title: Re: Tire pressures for "Classic" spec tires
Post by: RoyC on 27.01. 2021 17:46
Maybe one of those guages but with a rigid tube would be OK.


I think it would.
Title: Re: Tire pressures for "Classic" spec tires
Post by: Jules on 28.01. 2021 00:03
I use the rigid tube "push on" type inflator on my compressor for pumping up everything from cars to mulchers ( their tyres that is!), the only problem can be if the tyre is completely flat, in which case it pushes the valve through the wheel into the air cavity (its ok for tubeless of course), so then you need to grab the valve stem with locking pincer pliers while you pump the air in to get it started.....then I'm happy to use my old faithful sliding pressure gauge, again consistency is the key IMO.
A good example is my (very old!) yard tractor, I pumped the tyres up to around 30 psi using the gauge on the pump (30 psi recommended max) then went in for lunch and left it in the sun...........BANG! a front tyre blew out, when I checked the rest with my trusty old gauge, closer to 40 psi (admittedly with the hot air too!), lesson learned and $60 later  *respect*