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mountainbike fit compared to road bike fit----I know ...(6 posts)

mountainbike fit compared to road bike fit----I know ...David Ho
Jan 18, 2002 7:15 PM
that this is a roadie forum, but this is also a cycling forum above all.

I have not ridden my mtb in about 6 weeks until today.I have been doing base miles on the road and very low to med intensity.Well my mtb felt like i was riding someone elses bike, like the saddle was too low and the cockpit was weird.I did not make any adjustments, just continued to ride and endure the pain of the mtb ride.I got home and measured from center of BB to top of post and the mtb was almost 2 inches shorter than my road bike.Keep in mind that when I ride my mtb regularly it seems to fit fine, but it got me thinking--If I am training on my road bike and racing this with the saddle lower am I training muscles that I dont use as much on my mtb and does the saddle height make any diff when you are comparing 2 different geometries.I hope this made sense and those of you who do own mtbs can offer some insight!
re: mountainbike fit compared to road bike fit----I know ...dsc
Jan 18, 2002 7:38 PM
Hi David,

I, too, have been using my mtb on my weekday morning training rides. Since during the week I have to start my rides (currently about an hour in duration) before sunrise, taking the mtb means less worrying about flats, I can ride off the shoulder, hop curbs, etc. I take out my road bike Saturday and Sunday for the long rides.

I also had to raise my saddle about an inch or so to get the same leg extension as on my road bike. This also gives me about the same KOP position as the road bike. My reach to the bars is slightly different but the drop is actually more, as I have always set up my mtb in a fairly aggressive XC position.

Since I am still in the base miles stage of my training, I don't think riding the mtb 2-3 days a week will do any harm. Eventually, I will probably just ride my road bike during the week, too, and save off-roading for a 'fun' day on the weekend.

I am curious as to what insights others may offer, though. Anyone?

-Debi
re: mountainbike fit compared to road bike fit----I know ...xxl
Jan 19, 2002 2:49 AM
For what it's worth, my view is that proper riding position comes from the road. What I mean is that KOP, "flat" back, etc., are derived from a road rider's perspective (which is only natural, since road bikes have a little longer history than mountain bikes), and mountain bike "fit" is basically a compromise between road fit and the very real demands of mountain biking, e.g., the need to jump over/duck under obstacles necessitating a lower top tube. So, my approach is to set up my mountain bike so that it approximates my road machine, and then adjust from there as I need. I usually find that I have to lower the saddle a bit (a quick-release seatpost clamp is invaluable here), and the more heads-up riding position requires a shorter top tube/stem length. I guess you could say that, for me anyway, I try to set my mountain bike up so my riding position is as close to a road fit as I can get, within reason.

Having said that, I think you're probably doing yourself a favor by putting in the base miles on the road. Let's face it: "low intensity" miles, and/or lots of miles, aren't really what you run into when mountain biking, just by virtue of the terrain. But, those base miles you're doing are working your heart and lungs as well as your legs, and that is what you want. The road riding, esp. nice, flat, easy-spinning base mileage, may call some "extra" muscles into play, but I doubt that it's really that big a factor compared to the work you're getting on the cardio side. And if you want to work more "mountain-specific" muscles, just do some climbing on the road bike. My understanding is that the top-drawer mountain bike racers are all doing a lot of road work, esp. in the early season, to help build endurance, spin, etc.; similar to how top track sprinters do long early-season runs, even though they'll be focused on the speed later in their seasons.

BTW, saddle height does make a difference if you're comparing two different geometries, esp. if it's a "road vs. mountain" comparison. I'm sure you can find tons of advice on this board, but basically, the shorter top tubes of mountain bikes means that you're closer to the bars, saddle height being constant.
raise your saddle.colker
Jan 19, 2002 3:29 AM
why on earth would you race mtb with a saddle TWO inches below your ideal set up? unless you are ridin with your road saddle too high... do you set them based on le mond's formula?
sure you are not supposed to be as stretched on a mountain bike as on a road bike where your basic need is delivering power. you need to move all over the mtb and throw the bike around but pedalling with a very low saddle can damage your knees!
re: this happenscyclopathic
Jan 19, 2002 3:27 PM
when you go from one bike to another. make adjustments, rise your seat at least 1.5”.

btw what length cranks you run on road/mtb? if you mtb cranks longer (stamped on rear) subtract the difference. Most likely it'll be 5mm if so.

I am really tuned to position and I can feel diff in stack height from diff pedals and thicker shoes, 2" would be a killer.

try to set up your road/mtb identically same seat height, seat/BB offset and reach, otherwise you'd spend too much time readjusting going from one bike to another and it defeats the purpose. My 2 mtbs and 2 road bikes set up as close as possible. Diff frames, seat angle, TT, same fit.

everyone seems to pray KOPS. IMHO the impotence of KOPS overestimated. For those who disagree read The Myth of KOPS Ned Overend recommends to set mtb position 2 to 6cm behind KOPS gives more control.
What I've found going from mountain to road:Leisure
Jan 20, 2002 3:52 AM
The difference in a proper setup for each is in the handlebars.
When I got professionally fit for my road bike the saddle and pedal ended up being positioned exactly the same way relative to each other as they were on my mountainbike. This shouldn't be any surprise; it's just what's best for optimizing your power stroke. So my opinion is, unless you specifically want to emphasize certain muscles as part of an exercise regime, the more you can get used to keeping your seat higher on your mtb the better. Yes it can feel a bit more nervous at first on descents, but much of that goes away with experience and just standing up a bit. Later you'll get used to moving your whole body way back (ie- butt over the rear tire), and then any descent will seem doable even without a QR on the seat tube. A seat QR is more of a benefit when getting big air. I suspect the seat position is most of the reason your mtb suddenly feels foreign to you, unless you've got an older frame with some of what I'm talking about below.
For the handlebar you'll want the mtb's to be much higher and closer-in. It feels more confident on descents by allowing more mobility to move your CG back, which further negates the need to lower your seat. I think initially positioning the handlebar level to the seat is a good rule of thumb; it may seem high for a lot of road riders initially (heck, it seemed high for me going from my previous mtb), but get used to it anyway for a bit and then see how it feels going back. I don't think you're losing any pedaling efficiency either way, you'll just like the confidence of the higher H-bar. Getting a proper H-bar length is more problematic because on any given frame it can only be changed by changing the stem length, which affects handling on mtbs a lot more than it does on road bikes. If you've got an older mtb especially (when they were still running longish top-tubes), this is very difficult because a cockpit with a comfortable length will have a ridiculously short stem which makes the handling twitchy--kind of a contradiction. This among other things is why mtbs don't have the kind of established rules for proper fitting that road bikes do.
My suspicion on why road bikes are setup with the rider's torso more level: it made for small aerodynamic benefits that helped seasoned riders go faster. It probably took them a while to train the specific muscle groups that the position ends up emphasizing, after which the benefit was misattributed to being a biomechanical advantage.