Looking for tire size advice from fellow Trek SC gen3 owners. Recently bought a new Trek SC which came with 28mm tires (Conti gps5000 tubeless) on their oem Bontrager 51 pro wheels. After a few races, I feel something is not quite right, like something is “dragging”. Have tested with 65 to 85 lbs pressures. My 10 year old Cervelo P5 feels faster with old 23s(gps4000 with latex tubes). Would I be better of with 25s on these wheels?
These wheels are 23mm internally wide - you must NOT put 25mm wide tires. The minimum recommended are 28mm (+5mm) actually.
Look for improvement areas somewhere else, potentially in the position. It won’t be easy, as the old P5 is a damn good bike.
From the trek website:
Thanks for reply. Below tire info is on the Trek website. Really tough to find any info. And yes, P5 is great bike. Just thought time to upgrade. My bike shop is a great fitter and position is identical.
“Max tire size 28c rear, 25c front”
Following, lots of folks are running 28’s no problem. I’m currently running conti 5000 25 front and back (tubeless) on the stock RSL 51 wheels. Although I’m looking at upgrading to the HED vanquish pro 62/84 setup and running 25’s again.
I actually replaced the rear with a HED Vanquish Pro disc with the same 28 Conti 5000 tire. My bike times are actually the same between the two bikes, just feel much more energy expended on the Trek to maintain the same speed.
Do you have a power meter on both bikes? Are you using more power on the SC?
Dont have a power meter. But can just feel the difference. Definately using more power on the SC to maintain same speed. Legs are drained getting on the run. Not so after riding the P5. Only done Sprints and Olys on SC so far but doing KONA and trying to find solution soon.
Interesting, I would be curious what the power difference between the two is. Have you checked the hub and bottom bracket?
Yep, also changed bottom bracket when shop recently installed my new Rotor 54 crank from the oem 48. Bike has felt this way since new. Changed crank, tires, added rear wheel disc. No real change. Never rode with 28s before so thinking maybe that was it.
What is a “Rotor 54 crank”?
Aerodynamics is typically 80% of the cycling resistance. If you are slower I think you are more likely less aero on your new bike rather than rolling resistance causing the difference.
Same length cranks on both bikes? If yes, just sounds like a fit issue of some sort. If you are positive your fit numbers are the same, I’d get some PM pedals to share between the two bikes to verify your power output. It does not make any sense that the trek frame would be noticeably slower in any way.
“must”?..then why are the stock tires Bonti 25mm?
Scott
Sorry, thought it was a 54 tooth crankset. Its actually a Rotor 55/39 which bike shop replaced the oem 48 tooth Rival which was too small. Also replaced the Rival front derailler with SRAM Red. The Cervelo has an oem 52/39 Rotor crankset with SRAM Red front and rear.
Yeh, Trek recommends a 25 on front with the oem Bontrager 51 Pro wheels but the bike had 28s on both front and back when purchased.
Yep, same crank arm lengths on both. I’m wondering if its the front wheel? Have a HED disc on rear now but still have the oem 1625 gram front Bontrager wheel on where the P5 has 849 gram 8.9 Enves front and rear with skinny 23s.
You might have some problems shifting from a 39 tooth chainring to a 55 tooth chainring. Be careful.
I am pretty sure that the Bontrager front wheel does not weigh 1,625 grams.
I didn’t weigh. Just going by article I found online. “The Aeolus Pro 51 measured 1625 gram weight likely contributes to its relative lack of responsiveness, acceleration, and climbing ability. That measurement is with about 15 grams of tubeless rim tape and no valve stems. If you instead install the 60-gram per wheel plastic tubeless strips that Bontrager includes in the box, well, we’re getting into stock wheel weight territory.”
What bontrager front wheel weighs 1600 grams?!?! Don’t think so.