Help with Tyre Pressure

**Ragetty** · 17 Jun 08, 09:23 PM

Got a bit of a shock yesterday. Doing a few checks and measured the rear tyre pressure at only 28 psi.........! (it was measured cold).
Tyre 'felt' ok and I have not noticed any unusual handling. Thought this was a tad low so did some checking to find out exactly what the correct pressure should be. Handbook quoted 35 psi (2.2 bar) for the rear. However Bridgestone recommend 42 psi

for the tyre I have fitted - BT020R 170/60 ZR17. What do you all think? 42 psi seems very high.

**nogaromill999** · 17 Jun 08, 09:39 PM

28psi is ok.....we run 22 rear cold pressures on the BSB bikes when its hot weather.....normally run 31 front and 29 rear......

**zimbo** · 17 Jun 08, 09:58 PM

31F 32R for me, or 32F 34R with a pillion. 42 is way too high.

**Ragetty** · 18 Jun 08, 08:31 PM

Thanks. I was initially concerned but as I have had no handling problems at all could not really understand the higher figures quoted by Bridgestone and the Handbook. Panic over

**barry** · 18 Jun 08, 08:58 PM

I had the same concerns when I first bought my ss. Came from a fireblade [ 36f, 42r ] and thought it odd riding on tyre pressures that you could almost do by mouth

I run 32f, 34r and all seems well. Got to play with the suspension settings next.....only weigh 10 stone, so she's a bit firm....

**Ragetty** · 19 Jun 08, 09:46 PM

Quote:

Originally Posted by barry

I had the same concerns when I first bought my ss. Came from a fireblade [ 36f, 42r ] and thought it odd riding on tyre pressures that you could almost do by mouth

I run 32f, 34r and all seems well. Got to play with the suspension settings next.....only weigh 10 stone, so she's a bit firm....

Thx for the info. I have the same problem, weight just 11 stone. Suspension is set hard which makes it uncomfortable on poor roads but a dream when you really get going. If you soften it up to much you will be wallowing all over the place at higher speeds. Good luck experimenting

**michel couque** · 19 Jun 08, 09:50 PM

i find my bike,especially the front is very sensative to a drop in even 1 psi,for hard and fast i am finding for my 121/2 stone(plus a tiny bit too) 34 front 36 rear is perfect,but do differant tyres need differant pressures?

**NedLudd** · 19 Jun 08, 10:04 PM

[quote=michel couque;198291but do differant tyres need differant pressures?[/quote]

Absolutely. People always seem to use their Handbook pressures even though those are only applicable to the tyres the bike came with. Go with the manufacturer recommendation. Though I'm puzzled with the Bridgestone one in this case - it just doesn't sound right...

(If you can notice a drop of 1 psi Michel, vous etes un dieu.)

**Ragetty** · 19 Jun 08, 10:06 PM

Quote:

Originally Posted by michel couque

i find my bike,especially the front is very sensative to a drop in even 1 psi,for hard and fast i am finding for my 121/2 stone(plus a tiny bit too) 34 front 36 rear is perfect,but do differant tyres need differant pressures?

What tyres are you using. I have Bridgestone BT020 front and rear. Pressures are 26F, 28R. I have had no handling problems, in fact it sticks to the road like glue, never had a moment when I thought it would 'let go'. This is why I raised the issue, the handbook quoted 35R and the Bridgestone data sheet quotes 42R

I don't weigh a lot thou and have removed weight from the bike, so perhaps the pressures are ok for me. Tyre wear does not seem excessive either.

**Ragetty** · 19 Jun 08, 10:19 PM

Quote:

Originally Posted by NedLudd

Absolutely. People always seem to use their Handbook pressures even though those are only applicable to the tyres the bike came with. Go with the manufacturer recommendation. Though I'm puzzled with the Bridgestone one in this case - it just doesn't sound right...

(If you can notice a drop of 1 psi Michel, vous etes un dieu.)

Check out page 20 of the 2008 Bridgestone fitment guide, all 900ss models rear tyre pressure recommended is 2.9 Bar (42 psi)

Did not make sense to me either. If I put that pressure in the rear and it did'nt explode it would be like riding a zeppelin.

**charlieh** · 21 Jun 08, 02:46 PM

The bottom line is that the pressures recommended by the manufacturers are to give, more or less, optimum mileage for average weights of riders. This is why pressures are higher with pillions.

Lower pressures will in general allow the tyre to heat up quicker and run hotter. This in turn gives more grip, but reduces tyre life.

But....if the pressures are too low the tyre doesn't 'sit' correctly on the wheel and rears wheels in particular can spin inside the tyre....

....Not recommended

**michel couque** · 21 Jun 08, 04:42 PM

dear ned,i can only notice it on the front,maybe because that is supporting most of the weight of my tummy!

**billywiztheelder** · 21 Jun 08, 10:27 PM

When I fitted the 207RRs the manufacturer's recommendation was way over the handbook.

I use 33 front and 36 rear. Weighing only 66kg I do find the rear suspension hard. Bumps in the road will lift me out of the seat. Do I just wind the big spring back a bit?

**nogaromill999** · 21 Jun 08, 10:42 PM

Would that suspension adjustment were so easy billywiz.......think about it....you ease off the preload.....so the gas unit is under less tension now....so it may now need LESS rebound damping to allow it to extend at the correct rate, or more compression damping to prevent it from compressing too quickly. It all depends how good you are at interpreting what your bike is doing versus what you WANT it to do......

**billywiztheelder** · 22 Jun 08, 08:07 PM

Quote:

Originally Posted by nogaromill999

Would that suspension adjustment were so easy billywiz.......think about it....you ease off the preload.....so the gas unit is under less tension now....so it may now need LESS rebound damping to allow it to extend at the correct rate, or more compression damping to prevent it from compressing too quickly. It all depends how good you are at interpreting what your bike is doing versus what you WANT it to do......

Oh bugger, I supose that means I'm into checking sag and all that stuff. I have a step by step suspension setup somewhere that I will bone up on. Thanks Nog