Fitting Stages/4iii crank arm to RS500 BB?

[Rearviewmirror]

Hi all,

[EDIT UPDATED]

I've been riding for about a year now and starting to think about a new bike upgrade in the next 18-24 months. In the interim, I'm interested in getting a power meter so I can train more effectively outdoors - I've been training inside w/ Sufferfest and a Wahoo KICKR during lockdown. I want to buy a power meter that would be compatible with a 105-Ultegra/DuraAce setup for future compatibility once I buy a nicer bike.

I'm looking at getting a Stages or 4iii 105 crank arm and my BB is the RS500 threaded with the Claris FC R2030 crankset... I had originally thought it had a lesser bottom bracket, but am I now right in thinking all I need is the appropriate crank arm from Stages 4iii?

Is there anything I'm missing here?

Thanks a lot for any advice!

RVM

[Samuel D]

I believe it will work. However, you will likely need to use your existing left and right spacers with the new left crank. That may be obvious since the spindle is attached to the right crank, not the left; just making sure. And the Q-factor (tread width between pedals) will possibly be a little different. That is, your left crank may end up a couple of millimetres closer to the frame.

[Rearviewmirror]

Hi Samuel,

Thanks very much - so basically when I remove the old left crank, just make sure to use whatever spacers are already on there? Is the Q-factor something to worry about or not a big deal?

[Jamesh]

Not unless your Graham Obree!!!!

Cheers James

[Des49]

One of the easiest power meter solutions is the Garmin Vector 3 pedals. Just change pedals between bikes, only solution for some of us with older bikes where things like the Stages aren't compatible.

Just be aware many power meters can be troublesome, we have first hand experience of issues with Stages and the Vector pedals, when things work they are great, but otherwise really frustrating.

[Samuel D]

Thanks very much - so basically when I remove the old left crank, just make sure to use whatever spacers are already on there?

Right. Don’t remove the spacers just because a pair of 105/Ultegra/Dura-Ace cranks wouldn’t come with them. With the longer spindle of your Claris triple crank, you will need them.

Is the Q-factor something to worry about or not a big deal?

It’s a small amount, about 2 mm by my guess from the various spec sheets. But it will be asymmetric, with all of the reduction coming from the left crank.

When you check whether there will be room between the left crank and the frame for the power meter, you need to account for the new crank being a little closer to the frame. If this is likely to be a tight fit, don’t rely on my numbers above but try to find someone with a 105 (or whatever) crank to do a test fit.

Just be aware many power meters can be troublesome, we have first hand experience of issues with Stages and the Vector pedals, when things work they are great, but otherwise really frustrating.

Early Stages were poor but I understand the latest model has better sealing and signal strength. The 4iiii models are fairly solid. Garmin pedals have been problematic across all three generations for a whole range of reasons.

One of the most reliable options is the Favero Assioma pedals, which also have a really excellent iPhone app – kind of unbelievable for a hardware company and an Italian one at that. I used these pedals for about a year and was impressed by them compared to the functional and reliability problems my friends have had with other power meters. However, they are not currently in stock anywhere because Covid-19 took out their production, and they are a little more expensive than Stages and 4iiii now that those two companies have slashed their prices (because Favero was eating their lunch).

[Des49]

Early Stages were poor but I understand the latest model has better sealing and signal strength. The 4iiii models are fairly solid. Garmin pedals have been problematic across all three generations for a whole range of reasons.

One of the most reliable options is the Favero Assioma pedals, which also have a really excellent iPhone app – kind of unbelievable for a hardware company and an Italian one at that. I used these pedals for about a year and was impressed by them compared to the functional and reliability problems my friends have had with other power meters. However, they are not currently in stock anywhere because Covid-19 took out their production, and they are a little more expensive than Stages and 4iiii now that those two companies have slashed their prices (because Favero was eating their lunch).

Yes, the first generation Stages were appalling, the 2nd better. My Garmin Vector 3 pedals were eventually replaced by Garmin, 6 months in with the new pair and so far so good. But the warranty on the replacement pair is not good, so if I have more problems I assume Garmin will not just replace.
I would now consider myself an expert on dealing with the various issues with these pedals, but for such a costly item the user should not have to put up with this, does anyone test these things properly? If anyone needs to know - the baby oil trick really does help.

Interesting to hear your views on the Favero, seem worthy of consderaton if necessary.

[A1anP]

I’ve been using a 4iiii power meter crank (Shimano Ultegra) for nearly a year now without problems (touchwood lol). Actually, I bought a second one recently (105 version) to save the hassle of switching cranks between bikes.

A friend had Garmin Vector 3 pedals for a while and his Strava rides were filled with complaints about them playing up. He has since moved to Favero pedals and is much happier now.

The 4iii cranks are keenly priced at the moment e.g. Wiggle. I got mine from Mantel.

[Rearviewmirror]

Thanks a lot everybody - really appreciate the advice! Went ahead and ordered the 4iii Precision in 105 flavour from Wiggle! Looking forward to trying this out and seeing how power match works on my KICKR.