Chinese Ebay Carbon MTB Frame

Not not to ride in the wild but on the trainer.

For the last 4 yrs I’ve had an old (>10yrs) steel MTB frame on the trainer. I’ve always known the geometry is different to my “outside” hardtail MTB (seat tube angle is less steep meaning seat is approx 60mm rearwards).
I’ve always felt this riding and found riding outside “easier” but figured “no big deal”, however since getting a power meter I can now quantify it. I can roughly put out 20-30watts more outside

Off course some will be due to less heat, but I think most will be due to better bike fit / position on my outside bike.

I like a deciated set up on the trainer and the geometry on a £250 ebay carbon mtb frame is very similar to my outside MTB (with adjustment it will be within 5mm)

Has anyone done this and bought a chinese ebay special? My feeling is that it’ll be OK on a trainer and apart from having my outside bike on the trainer it’s the best solution.

Only other idea is to find a used steel frame (for the same cost) with similar geometry that I can use on the trainer (and outisde if needs be)

I wouldn’t attribute those 20-30w to a change of geometry but a change of environment: it’s quite common for a lot of folks to generate more power outside, and on the contrary there are a few who generate more power inside.

20-30w due to geometry may be possible going from a road to a TT position, but HIGHLY unlikely due to differences in HTA and reach that you’d find between various MTBs


This is the key. My outside bike is 73deg, saddle is foward putitng me right over the pedals, feels great.

My current trainer frame is maybe 66/67deg which even with the seat foward leaves me 60mm behind my outside bike. It feels alot harder to put out power being “so far behind” the BB.

I’m struggling to find an old mtb frame with something close to a 73deg seat tube.

I’m pretty sure it’s mainly the setup, the trainer is in an unheated garage, from Oct-Feb it’s often below freezing. I’m going to put my outisde bike on the trianer to check though.

The problems with trainers go beyond heating. Trainers typically don’t have any movement side to side as experienced outdoors, so you’re unable to engage certain muscles because the bike is more or less locked in place. My one friend was able to bridge the gap a bit with a rocker plate but still can’t replicate outdoor power indoors, I use the same bike on and off the trainer and my outdoor efforts are more powerful or done at a lower HR, typically both actually let’s you specify an indoor and outdoor FTP, and we have threads here asking for that functionality through TR on a regular basis

Depending on the bike & trainer…it’s not unusual to see a 20W difference between power measured at the pedal or at the crank arm and power measured at the rear hub. So if power meter A is an orthogonal strain gauge array on the crank arm and power meter B is an optical torque sensor at the rear hub I don’t think it’s way out of the ball park just to see a 20W difference. Especially if you have a SRAM 1x drive train. You’re just losing that in the drive train. Put your outside bike on the trainer, dual record, compare.

All that said, I’ve raced many, many 200/100/100k races on a chinese cyclocross frame. I’ve raced several dozen crits on a chinese frame. I’ve ridden for years on chinese wheels (linked on this forum a couple times before).

I cut up one of my gravel cyclocross frames to take a look at voids/delamination/wrinkles/bonding joints. It looked really good. Better than I expected.

So you can get some stuff that’s not a death trap, at least. But it can be a crap shoot and there are a lot of shifty characters in the biz.

I think it’s placement of the power meter + power meter discrepancies + you put out a few more watts outside.

The trainer measures watts at the “hub” most power meters measure at the pedals / crank / spider with no drivetrain losses.

You need to put your power meter / outside bike on the trainer and compare the two numbers.

That being said - I would not hesitate to buy a cheap frame. I have been doing the on / off thing lately and it’s annoying, but I haven’t wanted to buy the build kit for the rest of the bike.

I don’t disagree, but I’m surprised at the differance. Below is Baird (5 x 120% Vo2max) on the trainer

Any now outside a few weeks later (it wasn’t an outisde workout just riding a hill for 1min with the same RPE)

Both were seated and I realise there will be some differance due to temp, calibration, etc but 60 watts with a simlar HR and RPE seems alot.

I don’t know the answer but bike fit is different between the two and I’m wondering if I could have more effective training inside by getting closer to my outisde position.

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Think I have that frame, or a very similar one. Have raced on it a couple of times (local XC, nothing crazy) and generally ridden around on it a bit. No concerns whatsoever regarding strength etc. I’m not super heavy and I’m rubbish on a MTB, so don’t tend to ride very rough stuff though.

The only points to mention is that my frame seems to be designed to take a 2x chainset and the biggest 1x chainring I could fit is a 32, and that’s with bodging the chainline a bit. The other thing is that the paint/clearcoat seems quite soft and scratches fairly easily.

If it’s a round, offset seatpost could you just turn it around so that its offset forward and not back? Then maybe throw a long road stem on it so that the seat to bars distance is the same and slam the saddle all the way forward in the rails (ignore the ‘max’ lines on the rails). You might then struggle to get the saddle flat though but its probably cheaper and easier if you are able to make it work.

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A friend who owned an LBS ordered a bunch of carbon gravel frames from China and did custom builds with them. I bought one and went straight to a local bike park. If airing out over the jumps wasn’t enough to break it, then I think the frame is just fine.

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An evening on ebay shows you’re right, thank you. (The lure of carbon was strong, even cheap chinese carbon :grinning:)

For £80 I can get an old MTB frame and I’ve probably got enough spare parts to build it up close enough to my outside bike. I might even recoup a few £ selling my current trainer bike.

I tried that, the saddle ended up at something like a 25deg angle.


Came here to say exactly this. Why spend all that money on bike you can’t ride outside? Or one that you don’t want to be tempted to ride outside (for any reason why your main mtbs may be out of action).

Do you mean the saddle in relation to the ground? You didn’t push the seat foward past the flat bit of the rails did you? Just put it to the end of the flat bit. Maybe I’m missing a very obvious meaning but I’m struggling to think what else you mean by 25deg angle.
Even if your seatpost isn’t offset then you should be able to get most the 6cm by changing to a offset one that is pointed foward. Maybe different saddle like a fizik arione that is very long so you can sit further foward if the above don’t work. But dropping £250 you don’t need to and even just the extra wasted space having a junk bike…

I know what he means - even a round seatpost is designed to be facing a certain way. The seat clamp is attached not a 90 degrees to the post, but at maybe 107 degrees, to match up with a seat tube angle of somewhere around 73 degrees. Then there is a bit of angular movement possible to adjust to different seat tube angles and saddle angle preferences. But not enough to make up the original 17 degrees.

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Yep, I getcha now. Both my two latest bikes (so around 6 years ago and last year)both have seatposts where you could definitely get enough tilt so didn’t think about it, but understand now.
OP, could look into an eBay seatpost that would give you enough tilt? Still cheaper than another bike.

I’ve had a look, but due to the relaxed STA (67deg) I can’t find one. I’ve even used an inline post and with the seat foward it’s still 50-60mm behind where it would be on my outside bike.
But you are right, £300 is too much for a trainer bike, thanks to the advice I’ve found a few old MTB frames on ebay with a 73Deg STA for less than £100