Quick fit question - road vs MTB fit
Results 1 to 15 of 15
  1. #1
    RoadBikeReview Member
    Reputation:
    Join Date
    Aug 2015
    Posts
    518

    Quick fit question - road vs MTB fit

    Is there something about mountain bikes that changes the saddle extension you need? I set my seat height by feel and just measured--my CX and road are within 2mm of each other and my mountain bike is 15mm lower than my road. Even a few mm too low would give me knee pain on my road bike so 15mm is a massive difference.

    Is it something like the more upright position of the MTB changing my hip angle?
    I use the same pair of shoes, same model of pedals/saddle for all 3 bikes, and they all have the same crank length.

  2. #2
    RoadBikeReview Member
    Reputation:
    Join Date
    Dec 2006
    Posts
    4,211
    A lower seat height may be necessary for the lower rpm's generated on mountain bikes, or it may facilitate the engagement of the hamstrings-a smoother pedal stroke is more important when applying power on steep, rocky sections or anywhere it's critical to maintain traction.

    You may be setting your saddle low subconsciously so you can have easier, safer dismounts in rough terrain.

    I'm really reaching for an answer, because my saddle height doesn't vary among my road and mountain bikes.

  3. #3
    RoadBikeReview Member
    Reputation: Wookiebiker's Avatar
    Join Date
    Sep 2005
    Posts
    6,976
    My guess is it's your saddle set back … different seat tube angles, seat post set back and saddles will create different saddle positions. If your saddle is farther back on your MTB relative to your road/CX bikes, you will have to lower the saddle height to compensate for the further back position.

    A more upright position can make a difference, but generally only a few mm's, not a full 1.5 cm.
    Voting isn't marriage - it's public transport. You are not waiting for "The One" who is absolutely perfect. You are getting on the bus, and if there isn't one going exactly to your destination you don't stay at home and sulk - you take the one going closest to where you want to be!

  4. #4
    dcb
    dcb is online now
    RoadBikeReview Member
    Reputation:
    Join Date
    Jul 2008
    Posts
    753
    It also depends on what time of mountain biking you do. My mtb is more of xc race bike and I like my saddle very close to if not equal to my road bike height. I do like to get into more technical terrain as well and I just deal with it during those segments. But I see people who live for downhills on mtb's with the saddles an inch or two lower than the bars all the time.

    15mm does seem like a lot of drop.

  5. #5
    RoadBikeReview Member
    Reputation:
    Join Date
    Aug 2015
    Posts
    518
    Quote Originally Posted by Wookiebiker View Post
    My guess is it's your saddle set back … different seat tube angles, seat post set back and saddles will create different saddle positions. If your saddle is farther back on your MTB relative to your road/CX bikes, you will have to lower the saddle height to compensate for the further back position.

    A more upright position can make a difference, but generally only a few mm's, not a full 1.5 cm.
    Road/cx are 73-73.5 seat tube angle, mtb is 76 I think. The saddle is definitely a little further forward on the MTB, relative to the BB, but wouldn't the measurement from top of saddle to BB be the same? Like if the mtb seat was further forward relative to the bb, wouldn't I have to raise it to compensate to avoid pain and the painless height would be the same? Am I understanding that correctly?
    Last edited by thisisthebeave; 05-17-2020 at 05:36 PM.

  6. #6
    RoadBikeReview Member
    Reputation:
    Join Date
    Nov 2009
    Posts
    438
    Mtb is likely 66, not 76. If it were 76 you'd spend more time on your face than anything else.

    For my mtb I measure out the same sale height as road bike, then typically drop a few mm as it's good to have some extra leeway for movement without needing to activate the dropper.

    Sent from my Moto G (5) Plus using Tapatalk

  7. #7
    RoadBikeReview Member
    Reputation: Wookiebiker's Avatar
    Join Date
    Sep 2005
    Posts
    6,976
    Quote Originally Posted by thisisthebeave View Post
    Road/cx are 73-73.5 head tube angle, mtb is 76 I think. The saddle is definitely a little further forward on the MTB, relative to the BB, but wouldn't the measurement from top of saddle to BB be the same? Like if the mtb seat was further forward relative to the bb, wouldn't I have to raise it to compensate to avoid pain and the painless height would be the same? Am I understanding that correctly?
    Technically, yes … the further forward the saddle, the higher you would need to raise it (to a point).

    However, you stated head tube angle, not seat tube angle … even if it was seat tube angle it's not 76 degrees, that would be what you find on a Time Trial bike, not a MTB. MTB's tend to have a bit shallower STA, though some XC bikes are in the 74 degree range for smaller bikes.

    Also, set back includes your seat tube set back, which can differ from your road bike … generally anywhere from 0mm to 35mm of setback in the seat post.

    Also, a different saddle can sit farther back on it's rails than others.

    What you need to do is measure from the center of the bottom bracket to the front of your saddle (assuming the same saddle is on your road, MTB and CX bike). Drop a weighted thread from the tip of your saddle and measure how far back it is from the center of your bottom bracket (make sure the bikes are level). If there is a difference, that's probably causing the difference.

    If you use different saddles … measure to the back of the saddle.
    Voting isn't marriage - it's public transport. You are not waiting for "The One" who is absolutely perfect. You are getting on the bus, and if there isn't one going exactly to your destination you don't stay at home and sulk - you take the one going closest to where you want to be!

  8. #8
    RoadBikeReview Member
    Reputation: upstateSC-rider's Avatar
    Join Date
    Aug 2004
    Posts
    1,706
    I think you're not feeling pain on your mtb because you tend to move around much more (if you're doing it right) than simply pounding out mile after mile in basically a static position on a road bike.
    In reference to the Assault on Mt Mitchell...
    Quote Originally Posted by merckx56
    The easier solution is to find a biker bar in Spartanburg the night before, go in and pick a fight. The ass-whipping you'll get will be far less painful than the one Mitchell will give you the next day!

  9. #9
    RoadBikeReview Member
    Reputation:
    Join Date
    Aug 2015
    Posts
    518
    Quote Originally Posted by tfinator View Post
    Mtb is likely 66, not 76. If it were 76 you'd spend more time on your face than anything else.

    For my mtb I measure out the same sale height as road bike, then typically drop a few mm as it's good to have some extra leeway for movement without needing to activate the dropper.

    Sent from my Moto G (5) Plus using Tapatalk
    It is 76... Ibis Ripmo

  10. #10
    RoadBikeReview Member
    Reputation:
    Join Date
    Aug 2015
    Posts
    518
    Quote Originally Posted by Wookiebiker View Post
    Technically, yes … the further forward the saddle, the higher you would need to raise it (to a point).

    However, you stated head tube angle, not seat tube angle … even if it was seat tube angle it's not 76 degrees, that would be what you find on a Time Trial bike, not a MTB. MTB's tend to have a bit shallower STA, though some XC bikes are in the 74 degree range for smaller bikes.

    Also, set back includes your seat tube set back, which can differ from your road bike … generally anywhere from 0mm to 35mm of setback in the seat post.

    Also, a different saddle can sit farther back on it's rails than others.

    What you need to do is measure from the center of the bottom bracket to the front of your saddle (assuming the same saddle is on your road, MTB and CX bike). Drop a weighted thread from the tip of your saddle and measure how far back it is from the center of your bottom bracket (make sure the bikes are level). If there is a difference, that's probably causing the difference.

    If you use different saddles … measure to the back of the saddle.
    I fixed it. Meant seat tube angle

    I’m using the same saddle model and I did measure wall to BB and wall to saddle and the mtb saddle is a few cm forward. But wouldn’t I have to raise the seat on that bike enough to get the same extension so that the same spot on the rails to center of BB would be the same measurement?

  11. #11
    RoadBikeReview Member
    Reputation:
    Join Date
    Nov 2009
    Posts
    438
    Quote Originally Posted by thisisthebeave View Post
    It is 76... Ibis Ripmo
    Ha, yeah STB Vs HTB. you would rip less with that htb!

    Sent from my Moto G (5) Plus using Tapatalk

  12. #12
    RoadBikeReview Member
    Reputation:
    Join Date
    Oct 2013
    Posts
    4,019
    Your getting hung up on all the little details that are different and may not be the same, cause you don't know the difference from HTA/STA, rake, etc. Those are all going to be different. Just measure the BB, axis of the HB's @ the stem, rear of seat. Measure from wall and floor on all of them. If they are exactly the same, they are the same angles. If the stem/seat rails, seat setback, HTA, STA, etc are all differente, it don't matter. Cause the important dimensions where you sit and touch everything are the same. The internal triangle of these measurements need to be the same and the setups will be the same.
    If the mtn BB is 12" off the floor, and the road is 10" off the floor, the seat/HB need to be 2" higher on the mtn bike, get it?
    It really is simple, just ignore the little things that are different, as if these points are dimensionally the same, it's the same setup.
    Last edited by duriel; 05-18-2020 at 02:17 AM.
    BANNED

  13. #13
    dcb
    dcb is online now
    RoadBikeReview Member
    Reputation:
    Join Date
    Jul 2008
    Posts
    753
    Quote Originally Posted by upstateSC-rider View Post
    I think you're not feeling pain on your mtb because you tend to move around much more (if you're doing it right) than simply pounding out mile after mile in basically a static position on a road bike.
    This is a great point as well. I've had saddles that I can't use on a road bike that are OK for mountain bike and cross use. I've assumed that it's because riding off road is more dynamic and body position changes more frequently.

  14. #14
    gazing from the shadows
    Reputation: QuiQuaeQuod's Avatar
    Join Date
    Jan 2003
    Posts
    26,989
    Back in the 90s, my road and XC mtb position was just about identical. Upper body at the same angle, but my mtb saddle was just a BIT lower so I could get otb of the saddle easily.

    On my current MTB (santa cruz 5010), I sit very upright and the saddle is quite a bit lower. I'll put it up for long non-technical climbs. But normally it is as low as I can take without causing knee pain and still get power to the ground in a way that feels normal. How much lower, I have no idea, doing it by feel. 1.5-2 cm is probably in the ballpark for "baseline" riding. It felt super wrong at first, but since my knees don't seem to scream more than usual, right enough.

    So normal to have it lower, and I think that is more true today than in the past. FWIW.

    Position/geometry plays a role, I am sure, since a "trained bear on a bike" position makes it a lot harder to engage the hams. Plus more body motion, more standing, more irregular pedaling, more coasting. I doubt I would want to spin for 2 hours @90rpm on my mtb, even with the saddle up from where it is now.
    .
    Stout beers under trees, please.

  15. #15
    RoadBikeReview Member
    Reputation: OldZaskar's Avatar
    Join Date
    Jul 2009
    Posts
    2,330
    My saddles - road, gravel and MTB are within a couple mm of the same dimension - from spindle to top of saddle. I ride and race cross country... not downhill. I don't wear baggie shorts and have a dropper post ;-)

    Keep in mind, if every angle and dimension - height, stack, reach, etc. - were the exact same, you're still going to be leaning more on the mtn bike - because of the bar width.

Similar Threads

  1. road&mtb quick releases similar?
    By framesti in forum Components, Wrenching
    Replies: 3
    Last Post: 01-30-2013, 05:10 AM
  2. MTB quick release skewers for road bike
    By j73 in forum Components, Wrenching
    Replies: 2
    Last Post: 03-10-2010, 08:15 AM
  3. Does your road bike fit = your MTB fit?
    By gthcarolina in forum General Cycling Discussion
    Replies: 36
    Last Post: 01-05-2010, 08:33 AM
  4. Replies: 32
    Last Post: 02-02-2009, 02:57 PM
  5. Quick, Quick, Quick!
    By trek5900cyclist in forum Components, Wrenching
    Replies: 7
    Last Post: 03-30-2004, 09:41 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  

THE SITE

ABOUT ROADBIKEREVIEW

VISIT US AT

© Copyright 2020 VerticalScope Inc. All rights reserved.