Saris M2 tire trainer/tire questions

Hi all,

I’m a new Zwift user, and I’m just getting all of my gear together. (plus more coming I think)

So far I have a new Saris M2, I bought trainer tires for both mine & my wife’s bikes. (got a great deal on some Tacx tires), and I bought an Apple TV 4K, plus we’ve been using the companion apps too.

So I’m having a few issues/questions.

  1. When I use the Saris “clutch knob” the roller is crushed so hard into the tire, that I have a LOT of trouble just getting it to roll…Yes the tire is inflated to the max pressure of 100PSI, and no I’m not pushing in on the clutch knob while tightening it. (both of these things I’ve already read about)…so basically instead of using the “clutch” I’ve been tightening the roller until it contacts the tire, then going about 2 turns further…so far this seems OK, and I’m not getting any roller slipping, even under hard efforts.

  2. After each use, there is quite a bit of rubber? residue left on the trainer roller, I don’t “see” any wear on the tire, but that residue has to be coming from somewhere…so, what do you think is causing it? and should I be cleaning it off after every use?

  3. Since the wife and I ride entirely different styles of bikes, and run different size wheels/tires, do I need to do a “calibration” on the M2 every time we switch between bikes?

Sorry for the long first post, and thanks in advance for any help you can offer!

  1. Yes, that is how my M2 worked also, and I turned the clutch knob until it clicked. The M2 has a smaller flywheel than some other trainers in its category.

  2. I used a trainer tire and there is a small mount of transparent “glazing” on the roller.

  3. Probably unless your tires are inflated to the exact same pressure. I calibrated every ride because I didn’t pump the tires up to the same pressure every time, and temperature differences.

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Thanks for the reply!

I guess I’m at a loss on the trainer then, because when I crank the clutch knob until it “clicks”, it renders the trainer pretty much useless, I mean I’m not a SUPER strong rider, but I’ve got good legs, and I can put on miles, but with it cranked in “to spec”, I can’t even get up to 12-15MPH, let alone maintain it…

And as far as the residue, mine is well beyond glazing, I actually have to scrape it off with a finger nail…

You’re setting the M2 up as a power source, not as a speed source, right?
What’s your average power shown in Zwift?

Yep, it’s set up as a Power Source (and also, a cadence sensor & controllable device)…I’m not really sure how this thing can measure cadence, but I plan to buy a dedicated cadence sensor eventually, but until then, this will be fine I think.

I’m not sure where to view my past rides (to get my average power), and I’ve already ridden today already, and didn’t look at that number…But looking at the Strava upload for today’s ride, I had a “weighted average power” of 198w.

For today’s ride, I tightened the “clutch knob” 1.5 turns after contacting the tire, I experienced zero roller slippage, and had zero rubber transferred to the roller, I’m not sure if this is the “ideal” setting, but it’s the one I’m going to use until I figure this whole thing out.

…Despite this minor annoyance, I’m still really liking indoor training, hopefully that’s a trend that continues!

I am new to smart trainers as well and had used my M2 a dozen times and always felt like it was impossible to pedal. I recently found that tightening the knob until it clicked caused the frame holding the clutch knob to bend. Saris sent me a new frame and clutch knob assembly. I set it up and was told by support it should take 3 - 3 1/2 turns to click. It didn’t click so I just calibrated and rode at 3 turns. I contacted support again and I am getting another clutch knob assembly sent to me but was told it could take up to 4 1/2 turns depending on my set up. I don’t know what running it without clicking will do but I am kind of wishing I had tested a direct drive trainer first but I just ride for fitness.

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Yeah, I’m wishing I’d looked into a direct drive more closely too, but I’m just an amateur rider, I’m not training for racing or anything, plus my wife and I share this trainer, and we use entirely different bikes (1 MTB and 1 Gravel…obviously with trainer tires), we just needed a “simple-ish” way to stay fit over the cold/snowy months…and with Covid, I’d prefer to stay away from people for the foreseeable future.

I was trying to keep my budget around $500 so…I guess I’m a little underwhelmed what you get for $500 these days…

I’ve shot an email over to Saris, if I don’t hear back, I’m going to just cut my losses, try and sell this boat anchor, and I guess try a different brand (there goes ANOTHER $500+)…which, after reading more about the M2, and the LOL clutch knob, I wish I would have gone with a different brand anyway…

Troubling to hear so many problems with the M2’s clutch knob. I thought it was a good solution for the problem I had with the non-smart Fluid trainers - “is this tight enough?”

After a year of the M2, I just upgraded to a direct drive trainer. Once you get past the tire and wheel setup/issues, there seems to be no difference when riding.

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I am not truly understanding how a plastic knob can measure proper torque but I will try it and go by the recommendation of their support as to what to do. The ‘click’ concept was what sold me on the M2 but may be flawed. I don’t know if my wife would let me cut my losses and get direct drive.

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Yeah, I’m hoping Saris sends me a new clutch knob, as I suspect there is an issue with mine.

I really do want to like this trainer, it checked all of my boxes, and fit my budget, but this clutch knob fiasco as really soured me on this trainer.

However, I’ve been using the “1.5 turns after the roller contacts the tire” method for the last couple of rides, on both of our bikes…Still having zero slippage, and still not building up that rubber stuff on the roller, so I’m going to call this a “win” for the time being anyway.

So I rode at 3 1/2 clicks and then got the new clutch knob in the mail. I forgot to unscrew the knob after riding and went back and gave it an extra 1/2 turn to see if that worked and it clicked after turning it less than 1/16th of a turn. So i guess the knob works and I will keep the “newest” knob as a spare. My bike is on a wood floor and the kids are downstairs. I have a Saris type mat but have to figure out how to quiet things down.

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I’ve had my M2 for nearly a year and think it’s a good bit of kit. The clutch knob supposedly ensures a consistent amount of force is applied to the tyre for each ride but in my experience, so much force is required to make it click that it is unusable. My approach is simply to tighten it up until the tyre doesn’t slip when I rotate the wheel “enthusiastically”.
Similar to the OP, both my wife and I use this thing; she has a MTB and I have a road bike. I always calibrate it before I ride - bit of a pain but I think that’s just the way it is with this type of trainer. At the end of the day, it’s another 10 minutes of warm up for me…

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I’m glad to hear another person using this trainer the way that my wife and I do.

When you calibrate, have you been using the Saris app? Or the Zwift calibration?

I find that I can’t get the Zwift calibration to work, it just gets stuck/hung on step “3”…it’s done this multiple times, in fact I’ve never had a “successful calibration” using Zwift, I know I’m not alone there, I’ve read multiple things where people are having that exact same issue.

Whereas the Saris app has the calibration done in less than a minute (after warm up).

Zwift calibration has never worked for me, and I use the Rouvy app to perform a hot calibration on the M2. There’s an annoying amount of disconnecting/reconnecting that has to happen so I don’t bother opening Zwift until after calibration.

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Yeah, I’ve been “warming up” the trainer for about 10mins worth of spinning, then I fire up the Saris app, do the calibration, then close the app and fire up Zwift…I’ve never tried Rouvy, but I have 30 days free from Saris for buying the trainer, so maybe I’ll try it too.

However, I haven’t been calibrating before every ride…maybe I should start.

Clutch knob is a joke. I replaced mine with the older style cam lever from an old fluid trainer.

M2 works best with a 23mm tire at high pressure.

As long as the tire does not slip then the torque on the knob is enough. So rotate maybe 2 turns after making contact with the tire and you should be good. As long as tire pressure is kept high an droller and tire are clean you are good to go. Just ignore the clutch effect - waste of effort.

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Yep - I use the Saris App in the exact same way you describe below i.e. warm up the trainer for 5-10 minutes, open the Saris app and go through the spin-down calibration (takes about a minute). Then close the app and launch Zwift.
I used to then get connection problems where it seemed the trainer remained connected to the phone via Bluetooth so wouldn’t talk to Zwift. Since switching to Ant+ that problem has completely gone away.

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I have yet to run into those connectivity issues (I hope I don’t), but I run everything through the companion app because the Apple TV’s Bluetooth capacity restrictions are just annoying, 3 devices? And one of them is the dang remote? Really? … /Apple Rant

Just to add. Pump the tire up to 110-120 psi if it’s a 23 mm. Spindown time should be in the 4-10s range (as advised by Saris). Ideal for me was 5.5 s. My first clutch knob gave a spindown under 1s - joke. Second one was just over 2s - still awful. Third one I never used as I replaced it with an older roller cam knob from a fluid trainer. Just adjust the pressure until you get a spindown in the 4-10 s range after warming up and you’re good to go - shouldn’t get any tire slip as long as you’ve got plenty of psi in tire.


Our trainer tires are considerably wider…My tire is 29x1.25" and my wife’s is 27.5x1.25".

My 700c rim has an internal width of 19mm, so I thought the 23mm tire would be too narrow for that rim (which is why I opted for the 29x1.25)…and there was only one option for my wife’s 27.5 MTB rim.

And the max pressure per Tacx is 100 PSI

As mentioned above, I’ve been going with the 1.5 turns of the knob method, and so far it’s been fine…maybe I’ll go 2 turns, who knows.

I haven’t actually been watching the “spin down time”…I’ll pay attention when I calibrate before my ride later today.