Wheels,tires,tubes..Comparison..My Experiment..8 minutes

tim cronk

For those that always wonder if wheels,tires,tubes make a difference I thought I would post 2 recent comparison rides .  While not perfect the difference is significant enough to prove it does matter.  Unfortunately I can't narrow it down to which component made the most difference but it was 8 minutes over the IM distance.

What was the same-  Rider, clothes of the rider, helmet ,  bike , and the course (5 x out and back flattish for NH w/2700 elev change).

What was very similar but not exact - watts ridden, the way the watts were ridden , winds speed and directions

What was different- wheels , tires, tubes,PSI,  days , temperature and humidity.

Ride #1, 119 miles, 5:30:34, AP176/NP177, avg speed 21.6,  110miles in 5:07, 115miles in 5:20, FLO90/30 w/Conti 25's ,butyl tubes

Ride #2, 120 miles, 5:26:35, AP173/NP174, avg speed 22.1, 110miles in 4:59, 115miles in 5:12, FLODisc/60 w/Conti 23's, latex tubes

Summary- Ride #2 was 8 minutes faster over the IM distance on 3 watts less.... Was it the wheels, tires, tubes?  I don't know but 8 minutes on less watts is significant enough for me. See notes below for slight differences in power application (varied very little actually).

Notes: 

Ride#1 was ridden @ 172 watts for first 95 miles with a little below that for the first 50 and a little above for the next 45 , then 20 miles ridden at 194-200 before cooling down the last 4.... I ran 80 PSI in the butyl/25's combo on the Flo 90/30 set up... The day was cooler and I felt much better on this day.

Ride#2 was ridden @ 172 watts for the first 100 miles with a little above that for the first 50 and a little below for the next 50, then 15 miles ridden at 190-193 before 5 mile cool down.... I ran 90 PSI in the latex/23's combo on the Flo Disc/60 set up.... The day was hot and humid and I felt like crap.

 

Swanie

IM Maryland will be my first IM with aero wheel in the front and a aero jacket on the rear. My RR's with this setup has been faster than any ironman bike split I have done. I run butyl tubes and 23's front and back with Vittoria CX Evo (??). So I believe your results. Hoping for great things in two weeks.

Mike Roberts

I would have guessed that a 60/disc set-up would be at least 5 minutes faster over 112 than a 30/90, so I'm not surprised. I train on an aero set of 40s with butyl clinchers. When I throw on the 90/disc with 320tpi latex tubulars, the difference is immediately noticeable (like nearly 1mph). Just wish I had your motor to push them down the road a bit quicker.

Shaughn Simmons

Agree with Mike and would also add that going from 80 to 90 psi >10% improvement also contributes materially in addition to the other items......

Need to run a correlation coefficient on this one to categorically isolate the contributors......

 

SS

Al Truscott

Mostly the disc? Depending on the profile of the front wheel, the tire width is also a factor. Latex tubes … I have no experience with that, they don't make them in my wheel size.

 

Mark Maurer

Thanks for posting this Tim.I was thinking of upgrading my wheels with a Flo 60 front and getting a disc jacket from Wheel Builder for my PT rear wheel. It sounds like that might be a decent way to go.

robin sarner

Now try 25s on the disc/90 combo.

rbogle

Nice experiment. Seems to fit with other's experience and wind tunnel predictions. Here are a couple nice articles from Flo about tire pressure and about wheel combo efficiency:

FLO Cycling - Tire Pressure

FLO Cycling - The Great Debate - Aero vs. Weight *Edited

Lots of little things add up to significant free time and they don't have to be expensive...

jaleslie

Thanks Tim.  Very helpful.  

Peter Greagg

http://www.vittoria.com/en/app/
Vittoria suggests for their Corsa 320 tpi clinchers for Tim's likely weight plus his bike (55 - 65 kgs) for mixed road surfaces, 110 psi front and 115 psi rear.
For 75 - 85 kgs, all else being equal, they recommend front 115 psi and 120 psi rear.
In view of this, it would be interesting to see if Tim's times improved with higher tyre pressures?
Of course it could be the case that Contis are designed to have lower tyre pressures than Vittorias.

John Withrow

Thanks for the post. I ALWAYS go faster on raceday and I know my disc/808/latex tube combo has a lot to do with it. (I race on the Vittoria EVO)

I know you're a 'lil peep, Tim. But the first thing that jumped out at me was how low of a tire pressure you run. I understand if it's wet or bad roads, etc. but what's the rationale? 80psi sounds like a mountain bike. Must be a really soft ride. I'd be interested to see if there'd be any change in your speed (maybe not, but who knows) if you went up to like 105 in the front and 110 rear (especially in Kona where the roads are supposedly very smooth). With the latex tubes, the ride might not be as harsh as you think. I generally run 110/115 but I'm 180 lbs.

tim cronk

@Greg and JW the reason for the lower pressure is due to the width of the newer wheels (FLO 24mm)...A wider wheel has more volume so you need less pressure and then of course the 25's have more volume than the 23's.... Read the FLO data links that Rian posted... JW interesting you still race with Vittoria with all the data love for the Conti, I always loved the feel of the Vittoria better than the Conti, it just felt smoother, faster, better handling than the Conti, however I always thought that under hard braking the Conti's held the pavement better.

Disc/60 should be faster than the 90/30
23's are supposed to be more aero than the 25's
25's are supposed to have less rolling resistance than 23's
latex is supposed to have less rolling resistance than buty
PSI - debatable on the wheel, road conditions, size of the rider

But how much each of these really matter is difficult to test or prove. If all of them add up to 8 minutes or more (since the faster time was actually on less watts) then each change could only be 1-2 minutes each , not enough difference to really prove anything IMO since you would never know for sure if it was just the conditions on the day.. And this is over the IM distance.... Testing shorter distances would be preferable but then the changes would be even smaller and then even harder to believe for sure.

John Withrow

Just checked out the FLO tire pressure article. Interesting that since I use 700-23c tires and am ~180lbs, that chart shows I should ride at 112psi which is pretty much where I am anyways.

Re: Vittoria tires, I have done all of my races on them. And I really like them. I have seen the aero data on the GP4000s. But my whell/tire/tube combo just feels fast and great. I generally split faster in races than I should based on the power I put out but that could be from a whole number of different reasons. So even if the font would give me a slight areo advantage, I think the lower rolling resistance on both wheels at least offsets that and there is no aero effect of the tire on the rear wheel because my P5 frame completely covers it. re: the "hard braking" I really wouldn't know. It's a race, so I don't use my brakes. I feel the Vittorias "bite" really well when taking corners at high speeds, which as you know I love to do.

Any way you slice it, 8 mins is A LOT of time for an IM bike leg. So lurkers should take notice. Use fast wheels/tires/tubes if you care about more speed with less effort on race day!