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Discussion Starter · #1 · (Edited)
Hey guys,

New to the road bike forums, have spent some time over at mtbr.com, and made my way over here once I got interested in road biking too. I will be competing in my first triathlons this year, and though I know I want to buy a triathlon bike in the near future, I was thinking I'd hold myself off with/train using a set of slicks for the mountain bike for a little while. I have been trying lots of bikes and really want to get a Qunitana Roo Kilo, and though I could afford it right now, it might take away from other things in the next couple of months.

So I purchased some nice continental slicks from REI, threw them on, and tested them out. But the experience wasn't as pleasant as I had hoped from the reviews I have read. There was nothing wrong with the tires; the slicks did decrease resistance and make for a smoother ride.

Where the mountain bike fell short was above 30mph. I'm used to riding ~20-25mph with knobbies on my commute, but I've always felt that riding a mountain bike any faster would be like taking a hummer on the autobahn, and was hesitant. But all the talk about using slicks to see if you like the sport, etc., made me feel like it must not be a problem. I'm thinking it's possible that most people aren't going this fast, but when getting up in the high 20s/low 30s, the seat position and relatively high handle bars not only caused a lot of wind resistance, but made the ride feel really unstable. I tried to lean down as far as I could, but keeping my hands up high on the handlebars made it difficult. Also, presumably due to bike geometry, e.g. headtube angle, at high speeds the steering did not feel controlled; at one point my handle bars started to wobble from side to side (scary), but thankfully I calmed them down. I know moutain bikes are designed to be more nimble and make sharper turns, but again hadn't read about it being a problem at high speeds, even though I suspected it.

I knew the difference between a mountain bike and triathlon/road bike would be significant, but thought for sure that I'd be able to use the mountain bike with slicks for a little while. This ride made we want to drive to my LBS and pick up the Kilo tonight.

What should I do?

TIA, and sorry for the long first post :D

This was all on level road, by the way.

Oh, and how do we feel about the Kilo anyway?
 

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You're trying to fit a mountain bike for road bike purposes. You've made it work, but you've found out it isn't going to be ideal. How narrow are the tires? Are you riding these speeds on flat ground consistently, or are these achieved on downhills? If you are riding upwards of 25 mph on flat ground consistently with that bike, you should start racing now. You obviously don't need the road bike. :D
 

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Discussion Starter · #3 ·
Let's not forget swimming and running! :hand:

This was all on flat road, and the slicks are 1.5" wide. I guess I could try finding some disc brake road wheels, but I'm really itching for a road bike and would rather put the money into that.

So I've reached the ceiling on the mountain bike? Adding the issues I already knew about like gearing and wheel size to the issues I suspected and found confirmed the hard way like geometry/wind issues makes me feel like I should take the plunge.
 

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santos. said:
Where the mountain bike fell short was above 30mph. I'm used to riding ~20-25mph with knobbies on my commute, but I've always felt that riding a mountain bike any faster would be like taking a hummer on the autobahn, and was hesitant...

I'm thinking it's possible that most people aren't going this fast, but when getting up in the high 20s/low 30s...

This was all on level road, by the way.

I love speed posts like this.
 

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Mountain bike will work fine for your first few events, but eventually you will want to upgrade.

Oh, maybe you should calibrate your speedometer.

My recommendation is not to get a tri-specific bike, but instead get a road bike and clip-on aero bars. If you get into triathlons, you will want to ride on group rides, and tri bikes are forbidden on any sensible group ride. A road bike with clip-ons, if the set-up is correct, will give you the majority of aero benefits that come from a tri bike.

Cervelo Soloist is actually designed to be convertable from road to tri. The frame has an aero profile, and the seat post can be flipped, moving the saddle forward for tri.

But in truth any race-oriented road bike can be converted to tri use, if the saddle and bars are adjusted correctly.
 

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Discussion Starter · #9 ·
DM.Aelis said:
I love speed posts like this.
Thanks. Not sure how things are around here but I hope you're not judging a guy by his post count. At no point did I say I was maintaining 30mph, it was during short bursts. Sorry that I'm new to the road bike scene, and frankly hadn't seen these questions directly asked before and did not want to beat around the bush. Love it or hate it, I maxed out at 32.8 mph on flat ground, and the bike did not feel stable, so I'm trying to figure out if it's because mountain bikes shouldn't be going that fast on flats, or if I'm doing something wrong.

pretender said:
Mountain bike will work fine for your first few events, but eventually you will want to upgrade.

Oh, maybe you should calibrate your speedometer.

My recommendation is not to get a tri-specific bike, but instead get a road bike and clip-on aero bars. If you get into triathlons, you will want to ride on group rides, and tri bikes are forbidden on any sensible group ride. A road bike with clip-ons, if the set-up is correct, will give you the majority of aero benefits that come from a tri bike.

Cervelo Soloist is actually designed to be convertable from road to tri. The frame has an aero profile, and the seat post can be flipped, moving the saddle forward for tri.

But in truth any race-oriented road bike can be converted to tri use, if the saddle and bars are adjusted correctly.
Thanks for the recommendations. First, my speedometer is calibrated very accurately for distance, which I used more often than speed when on the trails. Is it not fair to assume that if distance is accurate, speed is too?

If a mountain bike should indeed be fine for my first couple of events, should I just be keeping it under 30? Or is it more likely that I need to practice maintaining stability at high speeds? Handle bars would probably help a lot (that one looks pretty cool Shawndoggy).

The Soloist looks very nice. I definitely see why opting for a road bike could be a better option and will think hard about it. I was thinking I would skip the middle man and go straight to tri, and hadn't thought about any downsides to a tri-specific bike. Road bikes seem cheaper, too...

Thanks again everyone.
 

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Triathlons are usually on fairly flat ground, and you generally want to maintain a fairly consistent speed. No offense, but I doubt you'll be averaging anywhere near 30 for any length of time, though I could be completely wrong. Unless there is something wrong with the bike, it shouldn't suddenly become unstable at 30 mph, either. Maybe you should have the shop check it out, looking for stuff like a loose headset, play in the hubs, etc. I have no problem believing that you can hit 32 for a short burst, but bursts like that aren't what you're looking for in a Tri. I would suspect that keeping an average speed over the Tri course of between 20 and 25 mph would be very respectable.

If you do want a Tri bike, get one used. There are always tons of Tri bikes for sale on Craigslist and Ebay because of folks who bought a nice Tri bike before ever having done one. They subsequently find Tris are not for them, and sell it soon after at an appreciable loss. Don't make their mistake.
 

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Discussion Starter · #11 ·
Don't worry, I'm pretty sure I won't be averaging 30mph. Am I wrong to assume that I might hit it a few times during the course of a race though? And I didn't wish to imply that all of a sudden at exactly 30mph my mountain bike starts to fall apart; just during my ride at speeds in the high 20s to my max I felt like the steering was not stiff enough and the bike geometry was making it exceedingly difficult to maintain cadence and keep the bike steady. And yes, I would hate to make that mistake, thanks for the heads up.
 

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santos. said:
Don't worry, I'm pretty sure I won't be averaging 30mph. Am I wrong to assume that I might hit it a few times during the course of a race though? And I didn't wish to imply that all of a sudden at exactly 30mph my mountain bike starts to fall apart; just during my ride at speeds in the high 20s to my max I felt like the steering was not stiff enough and the bike geometry was making it exceedingly difficult to maintain cadence and keep the bike steady. And yes, I would hate to make that mistake, thanks for the heads up.
It probably isn't the geometry, it's the gearing. I bet you don't have a low enough gear or a good enough pedal stroke to handle those speeds. Basically, even in the hardest gear on your mountain bike, you still need a very high cadence in order to get above 30 mph. You are spinning your legs so fast that it is making it difficult to keep the bike steady. This is of course just an educated guess.
 

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slicks etc

I've ridden many paved miles on an mtb with slicks (training for 24 hr races) and yes the handling feels funny at high speeds but I've always found that I can get used to it though. Your bike setup may not make that doable, dunno.

If it were me, this is what I'd do - I'd complete a few tris to make sure you like the sport (especially the swim training, which is what caused me to drop my Xterra plans, I HATE swimming) then invest in a TT bike if you are really serious about optimal triathlon performance and use the MTB with slicks for the group road rides to get intensity work in.

Cheers,
 

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SleeveleSS said:
You're trying to fit a mountain bike for road bike purposes. You've made it work, but you've found out it isn't going to be ideal. How narrow are the tires? Are you riding these speeds on flat ground consistently, or are these achieved on downhills? If you are riding upwards of 25 mph on flat ground consistently with that bike, you should start racing now. You obviously don't need the road bike. :D
no kidding...I wish I could averge 25MPH on my MTB. Hell...most of the time I can't averge that on my road bike. Above 30? That's hauling unless you're on a steep downhill or doing a quick sprint.

//I've gone dowhill on gravel roads on my Fisher Sugar at 45-50MPH and it was rock solid...maybe it's just the geometry of your particular MTB?
 

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Discussion Starter · #15 ·
SleeveleSS said:
It probably isn't the geometry, it's the gearing. I bet you don't have a low enough gear or a good enough pedal stroke to handle those speeds. Basically, even in the hardest gear on your mountain bike, you still need a very high cadence in order to get above 30 mph. You are spinning your legs so fast that it is making it difficult to keep the bike steady. This is of course just an educated guess.
Hmm. I don't have the cadence meter for my computer yet, but that seems reasonable. The highest gear ratio on my mtb is 44-11. I'm sure this is a pretty rough estimate, but I found this equation with a search:
mph = 0.07812 * cadence * chainring / rear cog
and solving for cadence using 32.8mph gives about 105rpm. Is that too fast to be stable at that speed? Or should I go practice some more? :p
 

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Discussion Starter · #16 ·
kretzel said:
I've ridden many paved miles on an mtb with slicks (training for 24 hr races) and yes the handling feels funny at high speeds but I've always found that I can get used to it though. Your bike setup may not make that doable, dunno.

If it were me, this is what I'd do - I'd complete a few tris to make sure you like the sport (especially the swim training, which is what caused me to drop my Xterra plans, I HATE swimming) then invest in a TT bike if you are really serious about optimal triathlon performance and use the MTB with slicks for the group road rides to get intensity work in.

Cheers,
I'm glad I'm not the only one who thought the handling was funny. Good to hear I should be able to get used to it. And good advice regarding triathlons, thanks.

Bocephus Jones II said:
no kidding...I wish I could averge 25MPH on my MTB. Hell...most of the time I can't averge that on my road bike. Above 30? That's hauling unless you're on a steep downhill or doing a quick sprint.

//I've gone dowhill on gravel roads on my Fisher Sugar at 45-50MPH and it was rock solid...maybe it's just the geometry of your particular MTB?
Over 30 wasn't maintained for long, probably only a tenth of a mile--I backed off after the handle bar wobbled. And I've been fast downhill before too, but pedaling on a flat adds an important element to the stability equation. Downhill I'm just holding on! :D
 

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santos. said:
I'm glad I'm not the only one who thought the handling was funny. Good to hear I should be able to get used to it. And good advice regarding triathlons, thanks.



Over 30 wasn't maintained for long, probably only a tenth of a mile--I backed off after the handle bar wobbled. And I've been fast downhill before too, but pedaling on a flat adds an important element to the stability equation. Downhill I'm just holding on! :D
check your headset/fork/front hub/stem for play.

Mtn bike should feel pretty solid at 30 mph and the wobble makes me think that something is loose. I've gotten up to 35-40 downhill off road on my mtn bike and it felt pretty solid so i would imagine that 30 mph on flat pavement should feel similar.
Are you gripping the bar too hard? That also can lead to some wobbles.
 

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cadence

That 's in the ballpark. I calculate about 110 rpm (your smaller tires make for a smaller diameter wheel than probably assumed by the formula you used). That's fairly fast, but nothing exceptional on a road bike -- lots of people sustain cadences like that for long periods, with no stability issue. I've hit about 150 rpm downhill on the fixie; I couldn't do it for long, but I wasn't unstable.

Most likely it's the upright position that's the major culprit. The speed wobble you describe is a different matter; it can happen on any bike, and some are more prone to it. It's a complex phenomenon.

You'll get somewhat better with practice, but that bike just may not ever handle well at those speeds.

And count me as another who's slightly skeptical of the speed reading. Did you re-calibrate your computer for the change in wheel diameter when you put the skinny tires on?
 

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It depends on whether you want to just finish the tri, or make good time. It may also depend on what distance you're doing. I'm facing the same issues with my first triathlon season this year. I'm going to start the season with sprint distance, but hope to be doing olympic distance by the end of the summer. I also have a group of friends that have been encouraging me to do century rides with them. So I kept the knobbies on the mountain bike & bought a road-bike on eBay over the winter.

Actually, I made up my mind to do this last summer when I rode a century (I did the metric option) with this group on a borrowed hybrid with road slicks. I kept up with the main group for the first 10 miles when one of the guys pulled up beside me & said "You know, you're putting about 30% more effort compared to us from the combination of your upright position & the smaller wider tires. Don't try to keep up with us or you'll be hurting later." Soon after that they picked up the pace & I dropped back. Toward the end of the ride I was cramping (this was partly a nutrition & hydration problem).

I disagree about staying with the mountain bike until you've done a few triathlons. I think you can find out if you like it by just doing "brick" training. A brick is putting all three events together for a single training session. I've been doing them weekly (almost) with a group since January. When the weather was bad, we did the bike portion on spin bikes. Later when the weather warmed up the others were on their tri-bikes & I did some hill work on my mountain bike (before the road bike was ready). Now I'm doing it with the road bike. My 1st sprint tri is in less than 4 weeks.

Sorry for going on so long, & good luck with your tri season.
 

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santos. said:
Thanks. Not sure how things are around here but I hope you're not judging a guy by his post count. At no point did I say I was maintaining 30mph, it was during short bursts. Sorry that I'm new to the road bike scene, and frankly hadn't seen these questions directly asked before and did not want to beat around the bush. Love it or hate it, I maxed out at 32.8 mph on flat ground, and the bike did not feel stable, so I'm trying to figure out if it's because mountain bikes shouldn't be going that fast on flats, or if I'm doing something wrong.



Thanks for the recommendations. First, my speedometer is calibrated very accurately for distance, which I used more often than speed when on the trails. Is it not fair to assume that if distance is accurate, speed is too?

If a mountain bike should indeed be fine for my first couple of events, should I just be keeping it under 30? Or is it more likely that I need to practice maintaining stability at high speeds? Handle bars would probably help a lot (that one looks pretty cool Shawndoggy).

The Soloist looks very nice. I definitely see why opting for a road bike could be a better option and will think hard about it. I was thinking I would skip the middle man and go straight to tri, and hadn't thought about any downsides to a tri-specific bike. Road bikes seem cheaper, too...

Thanks again everyone.
Hey yeah, sorry if it came across harsh. Just a little skeptical of the speedo is all : P

Don't sweat it. Regarding your OP, I'd say if you can self-gauge yourself as even slightly serious about pursuing this kind of thing long term, get yourself something that isn't going to hold you back.

Getting yourself a bike that inspires you and gets you in a strong aero position will transform your competition. If you are serious, I'd do it asap.
 
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