trainer tire pressure

aweber

Hello!
Is there anyone to help answer the following question:
I'm training indoors on a BBB QR magnetic trainer and I'm wondering how the tire pressure is going to affect resistance. I expect that the relationship is not going to be linear, that is the higher the pressure, the higher the resistance. Currently I'm switching between 70 and 110 psi and I keep roller against tire tightness constant (at 7 x 1/3 turns from the point the tire touches the roller).
Unfortunately, I do not have a power meter and spinning at given cadence will always give me the same speed, so it is really hard to tell the difference.
So, the simple question is: which tire pressure is going to give me more resistance, 70 or 110 psi?
Many thanks for help.
Andrzej

Pseudonym

the answer is - "it doesn't matter" - if you don't use a powermeter, then I'm assuming you use an HRM, that will give you a measure of your effort levels anyway. So long as tyre pressure is 'adequate' for the purpose (I use 90psi in mine) that's all that matters IMO. Just choose a pressure and stick to it.

Just to add the 7 & 1/3 turns from the point the roller touches the tyre sounds like quite a lot - I only use a couple of turns from the same point, just enough to stop any wheelspin. The resistance level and/or your gear/cadence should do the rest.

aweber

Hey, thanks for the quick answer. By the way, what is IMO?
Will try to stick to 90 too.
A

Pseudonym

IMO - in my opinion

aweber

LOL
A

MarcBC

My Tacx Flow says 6-8 bar for the trainer tyre and 3.5 turns on the pressure knob when the spindle is touching the tyre.

aweber

Thanks, my seven 1/3 turns equals essentially to 2.3 full turns on the pressure knob, compared to yours 3.5, which may mean that I have been using too little pressure.
A

Pseudonym

aweber wrote:

Thanks, my seven 1/3 turns equals essentially to 2.3 full turns on the pressure knob, compared to yours 3.5, which may mean that I have been using too little pressure.
A

sorry, I mis-read that earlier - I thought you meant 7 'full' turns...

aweber

Oh, no worries, I was obviously not clear enough.
Cheers,
A

John.T

Just use the same pressure as you would on the road. Too low pressure will cause tyre over heating due to deformation. You only need enough roller pressure to prevent slip. To get accurate results you should do a 'run down test' before each session. Spin up to say 20 mph and see how long the wheel takes to stop when you stop pedalling. Adjust by increasing / decreasing roller pressure.

aweber

Thanks for this John T. How long do you think it should take for the wheel to stop spinning? 15 to 20 seconds?
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John.T

That is rather long. I aim for about 5 seconds. The longer it takes the easier it is to pedal. The important thing is getting it the same each time.

aweber

Awesome! Will try your setup.
Thanks,
A