Tri Bars on a MTB

kenan

I'v got a cheap road bike and a 29ER MTB. I like the aero from the road bike but the wider tyres and disk brakes on the MTB. I could get a cyclecross bike but thought the 29ER was close enougth.

Has anyone tried fitting tri bars onto a MTB and was it any good?

cyberknight

I have seen it done .
Another option would be to convert the MTB to drops but it could be awkward in terms of pull ratios for the front mech as mtb mechs have a different cable pull apparently and brakes might need some tweaking .

The Rookie

Road and MTB cable brakes have different lever ratios, not good to mix them, if the MTB has hydraulics it's not really going to happen.

I've seen tri-bars on a 50's ladies bike with a basket, anything is possible!

Get some slightly narrower hybrid tyres as well, little point having aero bars with all that aero drag from the tyres!

RutlandGav

I've done it to about 3 diff mtb in my time. Partly for aero reasons, but mainly because i'm very prone to carpal tunnel syndrome. I've been off sick a couple days with a cold so downloaded a copy of the Sims to keep me occupied (sad git) ... now my hand is numb from gripping the mouse or kb or something.

I've avoided the issues with gear and brakes by just getting clip on aero bars. However, on my most recent bike this got a lot more difficult because almost all MTB bars taper away from the riser clamp. They have a smaller diameter than road handlebars to begin with, so I had to replace my handlebars as well for the least-tapered ones i could find to make it work.

It will really help you get confident with the setup if the recipient bike has lazy steering and a super stable feel.

Whilst I agree it would be mad to combine these with knobbly tyres, I personally want the fattest slicks i can get my paws on. I want oodles of grip to get me out of trouble when I mess up, and you'll be glad of every bit of bump absorption when you hit a pothole whilst resting on the bars. Braking isn't possible and the ability to change direction quickly are reduced.

Are the tyres really such a large component of aerodynamic drag? Suppose you fit ones 1 inch narrower, and have 29" tyres - that's 29 square inches off your frontal area. I just did a quick and very unscientific measurement, my chin is 12 inches lower on the aero bars, 12 inches x shoulder width 21 inch = 252 square inches off the frontal area saved by the aero bars. Not counting what is saved by no longer having elbows and forearms sticking out in the breeze.

Back in the noughties i saw a couple mph increase in my average speed on flat ground thanks to the tri bars. More than twice what i got going from knobblies to slicks, or any weight saving measure i could come up with.

Also, weight is more evenly distributed fore-aft on the bike. This reduces butt soreness as well as helping my wrists.

The Rookie

Clearly weight has no effect on speed in the straight and level, but yes tyres are really bad for drag, it's no just the area, but they have a high Cd due to the shape and the rotating effect and the effects of the tread road bikes use 23mm tyres for the lower aero drag over a 25mm despite having a higher rolling resistance.

kenan

Thanks for the input guys.

I'v got some slicks to go on the 29ER, larger volume 32c to give more comfort on the rough roads I ride. I'll see if I can get a cheap set of clip on bars.

I just found on the flat straights with the wind and my 740mm bars the headwind was a bit much compaired to my road bike.I have some sub 700 bars in the garage somewhere I'll fit while I'm at it and some bar ends (in for a penny).

cyberknight

I tend to ride with my wrists hooked over the tops , elbows bent in an aero position on my mtb on flat sections of roads anyway .
I should get a set of clip ons as well

ex-pat scot

Andy Wilkinson used to race 24hr TTs in the mid 90s on a MTB with aero bars. National champion multiple times, using that kit (he used to say that he couldn't get the position right on any other bike).

If it worked for him, then I'm sure it'd be OK on a modern 29er.
His biggest problems were tyre choice (26" rims = Specialized 26 x 1.0 or nothing else), and gear ratios (smaller wheels therefore needed larger rings)

The Rookie

Bar ends are really bad for aero, like a big parachute, grip the bars inboard of the controls to improve your aero, also flip the stem and use flat bars.