Trainer Tire Size

Post Reply
barry6054
Posts: 13
Joined: Thu Sep 11, 2014 3:02 pm

Trainer Tire Size

Post by barry6054 »

Hello all!!

I currently use a 700/25 tire on the road but I want to begin using an old tire and wheel for trainer workouts. However, my old tires are all 700/23s. Unless I overlooked it I don't see where you can change the tire size in trainer mode. Another thought is to create a separate profile for the different tire but can you do that in trainer mode?? Thinking out loud here; create a 2nd profile with the narrower tire, change the Newton to the new profile in set-up before going in trainer mode. Will that do it??

Thanks to all..Barry
User avatar
racerfern
Posts: 1356
Joined: Fri Jan 11, 2008 12:47 am
Location: Baldwin, NY
Contact:

Re: Trainer Tire Size

Post by racerfern »

IF you know what the difference is in Crr between the 23 and the 25 you could go into edit trainer settings and click on the coefficients tab. There is a Crr setting there. However, I think the difference is so minimal that you should just leave things alone. Remember, there is no "Cancel" button on this screen so be careful that you don't ruin an existing trainer profile. BTW, the 25 tire is about 9mm larger in circumference on average. I "assume" the tire circumference is set by the profile. You used to set this independently before the latest FW so the tire circumference under the newest FW should be as set by the profile. So yes, changing to the newer profile should do it.

Remember, in general your output on a trainer is about 10% lower than on the road so don't try to make on the road and indoor numbers match.
Fernando
barry6054
Posts: 13
Joined: Thu Sep 11, 2014 3:02 pm

Re: Trainer Tire Size

Post by barry6054 »

Thanks for your reply Fernando! Since it's such a small difference I'll just leave it alone per your suggestion. I was playing around last night with the coefficient tab but left everything like it was. And you are correct, I had to reset the trainer power adjustments. Thankfully I wrote them down earlier. Also, thanks for the clue regarding trainer power showing 10% less than outdoor riding. I knew there was a difference but didn't know how much.

Barry
jazclrint
Posts: 153
Joined: Thu Feb 25, 2010 8:05 pm

Re: Trainer Tire Size

Post by jazclrint »

I am in the same situation, 25c on the road, 23c on the trainer. So how has just ignoring the tire size difference worked out?

Another question is, in the places I live and have lived, getting a clean run at an ftp test is nearly impossible. Doing it on a trainer seems like a no brainer. But from what was said above, does this mean doing an ftp test on a trainer is pointless?

Thank you
'98 ProFlex 5500c under construction
'13 Schwinn Fastback custom build
'05 Bianchi Axis custom build
'13 Reline Metro Sport custom build
'15 GT Sensor Carbon Pro custom build
'?? A bike who's existence shall not be acknowledged
EHB
Posts: 129
Joined: Sun Oct 26, 2014 5:52 pm

Re: Trainer Tire Size

Post by EHB »

I wouldn't say it was pointless. Consistency is key. You can then see your progress.

Always do it on the trainer. Or always do it outside. There are lots of reasons that indoor is not consistent with outdoor anyway.

As an example last week I forgot to turn my fan on during treadmill intervals last week (twice). Both times my HR was 15bpm higher and it felt harder going. Made a surprisingly big difference.

And previously I've noted that I can do significantly greater power outdoors than in (DFPM in both). Not by anything stupid, but 15-20W.
Post Reply