sumbikerguy123

I have a 2004 Specialized Crossroads Hybrid. The triple chainrings are stock 48x38x28t with a 4-bolt pattern.

The Bottom Bracket is: TH Sport, square taper, 68mm shell, 113mm spindle, sealed cartridge.

The bike has a Shimano 7-speed HG41 (CS725) 11-28t cassette.

I want to see if I can get a bit more speed with a 50t ring, if compatible or available?

I lack knowledge in this area, so I'm not sure what, if any, options I might have here?

A compact crank would be nice, but...?

Any suggestions appreciated, thanks Sumbikerguy123.

Homebrew01

48x11 is a pretty big gear. 50 is 4% bigger. How fast do you go ?
I have a 53x12 (about the same as 48x11) and once I hit 40 mph or so downhill, I think I go faster, with less effort by tucking and coasting.

What model crankset ?

sumbikerguy123

R. I don't go fast at all on the hybrid unless I have wind to my back or going down a steep bridge, then its nice to have a 50t.

I don't know what model the crankset is, only info I could get from the Specialized Archives is: Specialized Forearm. I don't know what this means, if anything?

Best info I can give is in my OP.

Thanks!

Bezalel

The TA Chinook chainring is available in 50 tooth 104 BCD but it can be hard to find and will will probably exceed the capacity of your FD. IMHO it's a too big expense for such a small gain.

Edit: Just looked up the bike specs and I'd be surprised if the chainrings aren't riveted on.

sumbikerguy123

R. Thanks! My chainrings are hex bolted together.

My front derailleur is also bolted on, so it can slide it up or down to meet the size of larger ring.

I don't have calipers to correctly measure my BCD, but I rough measured with a ruler an looks like approximately 2.5" center bolt to center bolt across.

I'll check out the 104 BCD Chinook chainring anyway. What expense do you figure this chainring cost?

Thanks again!

ypsetihw

total waste of money, you won't really go much faster at all. you could easily spin up that difference by increasing your cadence. if you want to go faster, don't push a harder gear, push a smaller gear around more quickly. SPIN!

with that said, I would say find a bike store that has a spare parts bin, and buy a 53T chainring used for under $10, that way if you don't like it or it doesn't work, you won't be out much money. plus 53 will be different enough from the 48 that you will notice it.

also, tires make a HUGE difference. what kind of tires are you riding? smooth tread, narrow, higher pressure tires will have much lower rolling resistance than knobby wide hybrid tires. this change would make a bigger difference than 2 teeth on the chainring.

nfmisso

That is NOT the issue - the problem is the radius of the curve on the underside of the FD maybe to tight to work properly with a 50T front ring. Look up the specifications of your front derailleur.

My commuter runs a 52-39 double with a 14-32 custom 8 speed rear cassette to best suit me and my present commute. There is one hill I need to the 39/32 combination (with 35-622 tire). 52-14 (equivalent to 48-13) is only useful downhill or with a very strong tail wind.

cny-bikeman

For that 4% larger gear that you can only use downhill you will be raising ALL of your gears with that chainring by 4%, possibly making the 12 tooth slightly less useable as well. You will not go faster - if you can't manage to pedal 4% faster on the 48 tooth the 50 will not make you any more able to put out that amount of power.

CafeVelo

+1. I've be n riding my cross bike lately because the weather has been crap, large gear is 48/12. For general riding it's actually a more useful setup for me than my race crank, and have considered switching my other bikes, but when I'm flying downhill or in a fast pack I need that top end that's cut off by the 48.

sumbikerguy123

R. Vittoria Voyager Hyper 700x 32c tires, pretty decent tires.

CafeVelo

With a 4 arm spider it's definitely not worth your time or money. You'll spend a lot and get very, very little. You would probably feel more of a difference if you didn't use a touring tire.

sumbikerguy123

R. Basically why I would want or use a 48-50t ring for those rare times you would have a tail wind or going down a steep decline.

Thanks.

sumbikerguy123

R. Thanks.

sumbikerguy123

R. I felt quite a bit of difference with the Voyager tires over the stock sized 700x38c tires that came with the bike. The Voyagers are lighter, narrower, and roll a lot better/faster than the 700x38 stock tires and have almost a road bike feel to them.

What tires do you recommend?

Thanks.

CafeVelo

I recommend the best tire you can obtain, realistically in a 28mm for a hybrid wheel. A GP4000, vittoria open corsa, or any other top level tire will make a real difference in your ride.

sumbikerguy123

R. Try a 48/11.

NukeouT

Sprocket says its a Specialized Forearm Triple too Sprocket: Share

Google search says nothing specific about the BCD of a Specialized Forearm crank though. One way you can tell without measuring is by taking a chainring you know has a 130 or a 110 or whichever BCD and seeing if the holes line up.