Thursday, August 18, 2011


Three minutes and two seconds. That is an eternity when it comes to competition or any type of racing. That just happens to be the difference between my best time this season at our local cycling time trial, the Charlie Baker Time Trial that our club puts on in Concord, MA, and the time that I set last night.

The difference is that my best of the season was done on a full carbon fiber time trial bike outfitted with full aero fittings like a carbon fiber deep dish front wheel and matching full disc rear wheel and 23c tubular tires at 130psi. I was also wearing a skinsuit and an aero helmet. Last night, however, I was riding my full suspension (not locked out), carbon fiber 29er race MTB with traditional alloy spoked wheels and my 1.95" racing knobbies at 65psi. It is decidedly not aero. I was wearing a normal jersey and bibs and a normal helmet.

Oh yea, and I also got run off the road by a boat. Some douche pulling a boat got his truck past me, but couldn't get by Cathy when a car came the other way. He then decided to come back over into me while I was still beside the boat. I slammed the brakes on and went into a pavement cutout (had the right bike for that for sure), narrowly missing the big traffic barrel they had setup. He then wouldn't pass Cathy so I came back up along side of him on the right, pulled out in front of him, behind Cathy and passed her, then moving back to the curb. The dude wasn't impressed but WTF!? You can't just run my ass off the road with your crappy boat and then expect me to wait because you don't have the skill to drive the thing.

This bike just looks fast. What am I doing wrong?

If the three minutes and small change seems reasonable, maybe the average speed differential is more telling. The difference was between 27.03mph avg on the TT bike compared to 23.7mph avg on the MTB. Yes, that is more than three mph difference but logic would seem to suggest the difference should be bigger, right? I would certainly expect it to be as this is about as extreme a disparity as one could muster this side of riding a tricycle as a comparison. If I look at the comparisons for others, lets take Cathy for instance, who is a much, much better TT-er than I am, the disparity is much more pronounced with a near five minute and near 5mph difference week over week, TT to MTB. That, to me, seems like a more reasonable number.

This bike is fast, at least for an MTB on the road.

I realize that the MTB is my best discipline by a long shot and I am certainly the most comfortable on the MTB. Clearly this is translating to riding the MTB in general, in any circumstance. Maybe I should just slap some slicks and aero bars on it and see what happens. regardless, these leaves me pondering just exactly what the F I'm doing wrong on the TT bike. Is there some unlocked potential gain, hidden there in the god forsaken discomfort of that torturous TT bike?

I really hope so because I haven't made any gain in years. May be time to break down and go see Armand. We have been thinking about it for Cathy anyhow, who is looking for 21 seconds in order to knock none other than Karen Smyers out of the top 3 record times at the CBTT. Yes, Cathy is legit and deadly on a TT bike, as many unhappy men who get 'chicked' by her weekly can attest to. I on the other hand ...


Hill Junkie said...

It's easy to fall into the trap of linearly extrapolating times and speeds. But at 24-27mph, power is going almost entirely into overcoming wind resistance. Power is cubic function of wind speed. On the same bike, power increase due to wind resistance goes up about 42% from 24 to 27mph. The fact that you are less aero on an MTB is big deal, but not that big when speeds poke into the high 20's.

I am impressed with your speed on the MTB though. That is wicked fast no matter how you analyze it. Perhaps some fit optimization or more time in the TT position would net you more speed.

gewilli said...

#1 positional differences will greatly affect your power. If you aren't recruiting the same muscles you may not go that fast.

27 is wicked f'n fast. You've seen the times from the TT down here maybe.

Looking at the TT bike i'd say the bars are way too high.

The difference between the two avg speeds is pretty dramatic as Doug mentioned.

If you were to set the saddle position relative to the BB on the TT bike to be the same as the MTB, you might be able to get closer to the Jonny Bold TT times.

mkr said...

Actually, the bars are about 10" lower than the saddle, which I think is the biggest issue. Too aggressive and I can't produce the power. The saddle has traditionally been near the normal road angle (nose was 6.5cm behind the BB). I changed that recently to no gain so I'm going to slam it back. The bike doesn't fit super well; I wish it were bigger. My PR is two minutes off the record time. I'd really like to trim that some.

jay robbins said...

that seems like a pretty crazy difference. do you have an power data from the TT bike that you could send me? i have an aero calculator for the CBTT that i could run it through if you want.

gewilli said...

i got thinking...

always a bad thing I know

but i'm going to wager that you are way too stretched out on the TT bike.

dropping the bars would also require moving them closed to you, i've been looking at lots of TT stuff over the summer, pro position and what not. Certainly not with Speed Merchant's wind tunnel eye, but I ain't new to this gig.

Jonny Bold said...


Come down to the Cape and have Georgey at Corner Cycle get you dialed in, position wise. His expertise in bikefitting is second to none. He uses old school and new. He also takes into consideration our old less flexible backs. What works for the Tour de France riders, doesn't translate well to us old farts, that haven't been riding a bike for a living for 15 years.

I'm still pretty impressed with your mt. bike speed though. Damn! Some of our road races don't average that high.