|Road vs. Mountain in a battle to the death!||Ahimsa|
Oct 10, 2002 3:36 PM
|Nah, not really...but I would like to know if someone out there with knowledge of the differences in frame geometry between the two could give me a "compare & contrast" primer. What with manufacturers all doing different things, it's hard to distill a real trend amongst the mess. Especially for me with my miniscule MTB knowledge.
So, road frame vs. MTB frame geometry and the needs/effects thereof?
Care to take a stab?
|First you gotta||Mel Erickson|
Oct 10, 2002 5:08 PM
|define what type of MTB you're talking about. Hardtail, softail or full suspension? For hardtails they're more like a compact road frame. Top tubes are generally shorter because the position is more upright. Because you move around on the bike so much more the frame dimensions are less important than on a road bike. You'll likely be able to fit a wider range of sizes. Handling concerns are quite different. You need to be concerned with pushing in downhill corners and traction on uphill climbs. Do you want to freeride or do XC. Totally different bikes with totally different handling characteristics. Downhillers want HEAVY, burly bikes with lots of suspension travel (they don't bother to ride them uphill, just take the lift). Because of the variety of bikes for the variety of riding it's much more difficult to choose and peoples choices are typically more individual. There aren't really any fit formulas and you really have to test ride to find what you're comfortable with. I won't even go into frame materials because it's so overshadowed by the hardtail/full suspension debate (and full suspension makes frame material a lesser issue). Now, what do you want me to expand on?|
Oct 10, 2002 5:53 PM
|I'm thinking of a hardtail, non-suspension fork MTB (steel for sake of comparison) vs. a steel roadbike.
Just the lengths and angles and the reasoning behind it all.
Oct 11, 2002 1:07 AM
|I'll assume you're comparing an XC level bike to a road bike.
1) slacker head tube
2) less fork rake
3) wider handle bars
Result: slower but more steering stability.
4) relative longer top tube
5) longer chain stays
6) larger wheelbase
Result: rider weight is better centered during ascends and descends, less risk of endo or lifting.
7) seat tube sometimes clacker
8) BB farther forward
9) longer cranks arms
10) smaller wheel size
Result: favors more pedal torque and acceleration at slow speeds
11) higher BB
12) less BB to chainstay drop
Result: more ground clearance and eases leaning the bike for cornering and slow speed balance.
13) I'm sure I've missed a few obvious points
Result: possible ridicule and flame bait :)
|Back in the day, they weren't that different||Geardaddy|
Oct 11, 2002 7:05 AM
|Your list is a pretty good summary, but there is a lot of variation out there now with the different manufacturers.
The "retro" geometry seems to be gone though. My first mountain bike, a mid 80's Bianchi, had a geometry not unlike a road bike. A friend of mine has a late 80's Bontrager MB2 which is of the old school geometry as well, and is really a joy to ride. The shorter wheelbase and steeper head/seat angles make the bike a great turner in the singletrack, and the bike climbs really well. It just takes getting used to the "imminent endo" feeling when on a fast descent.
Oct 10, 2002 6:05 PM
|Hardtails do not generally have shorter top tubes compared to other bikes. There are race geometries that use a longer top tube to stretch out the rider. Some such as GF use a shorter top tube but longer stem to accomplish the same thing. As for the geometry not being important, have you ever ridden similar sized bikes with different headtube angles especially? Quite different animals. There are even full suspension bikes with a stretched out ride, like the GT I-Drive Race Team bikes of a year or so ago. As for fit, you will want a MINIMUM of a couple of inches of standover height for any tough offroad riding. As for stretched out/upright positioning, it is a personal preference. If you ride lots of tough climbs, you will like the more stretched out geometry, as it will keep your weight over the front and allow the wheel to track better. If your rides are less hilly, then a more upright position is not so bad. Bottom bracket height is a big issue as well. BTW I do own a steel 29'r as a commuter and Burley hauler, a 3.5" travel (f and r) full suspension aluminum framed ride, as well as a road bike. I find that the seating position is close between the fs and the roadbikes, while I like the more upright ride of the steel bike. It makes is a nicer ride to work or pulling the rug rat around.|
Oct 11, 2002 5:41 AM
|I wasn't saying hardtails generally have shorter top tubes compared to other MTB's but to road bikes and it can be difficult to even compare top tube length because of the variance in other factors such as design(you mentioned the GF as an example, add bent TT's, etc.) You have to compare effective top tube length and alot of manufacturers don't list this. The variance in cockpit length is much greater in mountain bikes than road bikes and riding terrain and style play a much more important role in selecting a bike than for road bikes. I guess what I was trying to get at was there are MANY more variables to consider when selecting a MTB than there are for a road bike.|
|quite true ! :o) NM||IAmtnbikr|
Oct 11, 2002 8:39 AM
|re: Road vs. Mountain in a battle to the death!||Breakfast|
Oct 10, 2002 6:49 PM
|First of all, I'm not a framebuilder so I'm just going to state what are the logical differences to me.
Number one is the wheelbase, then the size of the contact patch of the tires. Then there is the diferences in steering geometry, my guess is road is a quicker geometry. Now there is the rider position, more upright on mountain bikes. Also, there is the balance or weight ratio between the rear and front wheels, my bet is the MTB has a bias more towards weighting the rear wheel.
I don't really know but those are my takes on the two. Please, if anybody can shed more light on this I'd be happy to read it.
|and.. why are you asking?||cyclopathic|
Oct 11, 2002 7:02 AM
|are you turning to dark side? 8-P|
|Ahimsa, I am your faaather! nm||Mel Erickson|
Oct 11, 2002 10:17 AM