Sore on the quadriceps femoris.
When I put the roadsaddle on the same height as on the mountainbike I get saddle sores.
Sore on the quadriceps femoris.
Yes I was riding mountainbike more. Maybe the flat bars have an impact.
- That is a dangerous assumption. At the least, you need to consider the reality that each power meter has a power data tolerance, and if the two are stacked in opposite directions from the “real” number, that could be a notable portion of the difference. Until you do testing to compare the two, you must keep that in mind as one variable in the discussion.
To your main question, it’s all but impossible to evaluate this without more details, to include pictures and/or video of you riding both bikes. Essentially, it’s best to consult with a bike fitter so they can evaluate your fit on each bike.
Do you use the same saddle on your road and MTB? I have the same saddle on both of mine, Pro Stealth. Also are your crank lengths the same? I swapped mine out so I have 170’s on both.
Can you share some more details about these measurements? For how long are you holding that power? Is it indoors or outdoors? Is it an average power over an interval or a ride, or is it normalised power?
Is your example from attaching these two different bike to the same trainer?
Over what period is your example, 20mins? 1hr?
There will be a difference between different power meters, how different you can only find out from testing.
I would suspect wider stance (Q Factor) on the MTB vs. road bike.
Some folk are more comfortable putting out more power in a different riding position. I don’t mtb myself but I put out more power dancing (figurative speech) on the pedals of an upright road compared to an aero position on a TT bike. So some differences on different bikes is to be expected add that to the difference in power meter it can be substantial. Both pm may be accurate to +/- 2-3% but if one reads low and the other high the difference can be up to 6%
That’s taking into account static sag on the MTB, right?
What? Assuming a person measure saddle height in a typical way (Center of Bottom Bracket, along the Seat Tube Angle, to the Top of the Saddle), suspension sag is irrelevant.
- Sag would only matter if someone measures seat height from the ground, which is a bad idea IMO.
I just want take a moment to show just a few of the potential fit related issues here. It is far more complicated than any single dimension given above.
Saddle Height (Taking into account differences in saddle, crank length, Q-factor, shoe/pedal combination, pedaling style differences between road & MTB, etc.)
Saddle Fore/Aft (Related to above, with likely differences related to body position for bike handling, that lead to power variation as well.
Handlebar Reach/Drop (Relative position from saddle to hands, with includes final Reach & Drop position, as well as width and hand orientation).
All of the above lead to a functional body position that can have a direct impact on the RPE and output from the rider, as well as comfort and injury issues (like the sores).
- Also absent from the OP is sufficient detail about the comparison other than power & heart rate. Questions about the terrain use for each comparison are relevant. Differences in relative pitch and even surface condition can lead to notably different rolling resistance, inertia and relate demand on the rider.
- Cadence is even a notable factor that must be matched if you are using heart rate for comparison. It’s variable on it’s own from all the influences we know, so matching conditions on the bikes as much as possible is the only way to have even moderate confidence in HR as a comparative data point.
Essentially, this is way more complex than can be summarized in a few sentences, and requires lots more info from the rider on the testing and bike setups.
Agree, before going into any fit related issues, its worth checking that there is an actual power discrepancy and not just a bad comparison between two rides.
Yup, I pointed that out as well, specifically because the OP brushed it under the rug.
I’m vaguely recalling a mountain bike I had where I had an issue where the saddle felt way too low - I then realised when sitting on it I was compressing the suspension, effectively shortening the seat tube. Hopefully I’m not imagining that!
It was a bike similar to this, from a glance it looks like that would happen here?
OK, that is a fairly unique issue AFAIC. What you show there is the old URT (Unified Rear Triangle) suspension, that did often move the BB with respect to saddle height. It was an option early in the development of MTB suspension, that is all but missing in the modern MTB full suspension world. I can’t even think of a bike that has been built upon that design in the last decade or longer.
You are correct, that it can have an impact on setup, but it depends on the specifics of the URT design. Some actually didn’t have much BB shift WRT saddle height. I chose to ignore that possibility since this suspension design is VERY uncommon these days. If the OP happens to have one (via a very old model), then the concern is valid. But I would put $10 on the fact that he has a more modern bike without a URT suspension.
Not to mention that the OP has not even clarified the details of their MTB. Could be a hard tail for all we know. As above, many missing details here.
Back in the day, I took one of our prototype frames up to Steamboat Springs for a weekend of chairlift riding. Not really knowing much about the concept at the time (wasn’t yet in the product development department), I was massively disappointed. As soon as you got off the saddle, the suspension is essentially eliminated…which if you are just doing downhills kinda sucks!
For the time, it effectively addressed what was seen as the major drawback of FS bikes…drivetrain efficiency. At the end of the day, however, it was a design that was ultimately slower than most other active FS designs because of the aforementioned issues when coming downhill (or over technical sections).
Yeah, fun times. I started in MTB in 1992, and spent way too many hours following and testing bikes of as many suspension designs as I could get my hands on. The URT was interesting, but the wrong solution to the right problem if there ever was one.
A local friend has a personal museum, and he is also a major Schwinn guy. He’s got several SS bikes, a GT i-Drive, Klein Mantra and I think even a Trek Y bike. Not many people have that much of a bike collection, let alone about 80% of the most common URT’s from that dark era
Fun bikes to revisit, but it doesn’t take long to remember why most of them never get ridden now.
Just found this website, which is a nice stroll down memory lane. This page does a good job explaining the evolution of the SweetSpot design, from the original design with bearing in the pivot to the later oversized bushings.
Lots of other good stuff in there as well…even the old Sting-Ray snowboard! (I still have one up in the garage).
Didn‘t read through the entire thread, but found „Peak Torque‘s“ Video on power on Fully bikes interesting. The power meter might show the same power for a locked out suspension and a open suspension, but you are climbing at different rates. The open suspension has the power meter over read… for more insight, it’s better to just watch his video:
Sorry if this had been discussed earlier.
So, additionally to the more upright position (and maybe better physical adaptation to riding that position), the PM on the MTB might also be playing tricks.
We haven’t jumped in to that level, largely because we have no idea what MTB they even have, and if it even has rear suspension.