Stromer ST1 Platinum Larger ring size?


New Member
Has anyone put a larger ring on the platinum? I am spinning out at 28 mph and have a lot more room physically to give. I bought my wife the ST1T and I can easily make 30 mph on her bike. Anyway your thoughts or lessons learned are appreciated :)
I also have a ST1 Platinum, but wanted to go to a smaller chainring for the super steep hills I climb. I was warned by the bike shop that my front Derailleur would not work too well with a larger gap between chainrings. They told me I would have to go down from my 50 tooth to a smaller ring if I wanted to put a 28 or smaller ring on the front. So I guess you could go up to something bigger than your 50 tooth chainring, but you may have issues shifting unless you also go up as many teeth on your smallest chainring too.
Your ST1t has the Schlumpf drive right? With a 30 tooth chainring? Isn't there a button on the side of the crank that increases the gear ratio? Which should increase the ratio to something more like a 45 tooth chainring. A 45 on the front with 11 on the back at 30mph is slightly over 90 cadence. Is this considered spinning out? Not sure if my math is right, but maybe you could provide some more information.
Check that... the Schlumpf speed drive has a 1.65x overdrive ratio, which would take a 30T to a 49.5T. 49.5 on the front with 11 on the back @ 30mph with 26" wheel is a cadence of around 86/87. Doesn't seem like a spin out. If you leave the speeddrive on the 30T, then at 30mph the cadence is 109. This is very fast for most people.


Platinum is spec'ed with a 50/39/30 triple. It looks like a 130 BCD crankset. I suspect you could probably find a Shimano 6503 crankset and salvaged the rings for pretty cheap. They came in 52/42/30 configurations that should swap right. You'd need to raise the FD a smidge probably. If only adding 2t to the top chainring, maybe you can get away without replacing the chain due to chain wrap.



New Member
Wow! Thanks for all the helpful information everyone! I did make a change to the torque sensitivity (code 1004). It was set to 50 and I set it to 70 and it has made the ride much smoother. Although, the range may be effected. I think a triple set with 52t on the late side is the next step. I'll let you know how it goes.