Is a larger rear sprocket bad for my bike?

Dan85 · 07-01-2009, 04:47 PM

Not sure if this post is in the right section but here's my question: I bought my bike used and the guy had a larger back sprocket on the back so he could do wheelies easier/going slower. I think he said it was still the stock front sprocket but I'm not sure I havn't looked, the back sprocket is probably at least 3 teeth larger, it is a lot bigger than the stock sprocket. He gave me the stock sprocket but it is worn down and not worth putting on. I was going to order stock sprockets to put back on the bike because I don't wheelie the bike. My question is how bad is it for the bike to run at higher RPM's consistently because of the larger sprocket. I don't do a lot of riding in stop and go traffic most of the speed limits here are around 40-45 but when I got riding I usually find 60-70mph to be a pretty comfortable cruising speed, and I usually am around 70mph on the interstate as well. If I am going on longer distance rides or riding at higher speeds is it better for the bike to have the stock sprockets on? The bike currently tops out about 123 mph to give you an idea of how much larger the sprocket on it is. I think the stock top speed is about 151 or so which is what I see from youtube vids. 50 mph on the bike is about 5 1/2 grand RPM's but I see it get to 8-9 RPM's when I am cruising around or driving interstate (freeway).

Dr.K · 07-01-2009, 10:01 PM

No its not bad for your bike. But it does throw your odometer off and the bike says its racking up more miles than your actually doing.

hybrid · 07-02-2009, 08:03 PM

wont hurt it but annoying for street bikes if its that bad.

I think your bike still used the speedo cable on the front wheel so if thats the case, youre fine the mileage will be as accurate as it can be.

kevin_stevens · 07-02-2009, 08:07 PM

If those speeds are accurate he made a bigger change than +3 rear. Sounds like he dropped a tooth in front as well. That *will* decrease chain life somewhat as the chain has to make a sharper bend around the smaller sprocket. I'd at least confirm what's on there and go back up on the front if necessary.

KeS

(+3 rear would be about an 8-10% gearing change on most bikes, and your speeds reflect at least twice that amount.)

Dan85 · 07-03-2009, 01:04 AM

Thanks for the input guys. I found a decent price on ebay for a stock sprocket/chain set and went ahead and ordered it.