rzhunemagu

Currently have FSA Dyna Drive 48/38/28 on my Trek 8.3 DS and need to get it replaced. Was looking at Shimano T551 but seems that none of the US retailers have it available or its an old model.


Any recommendations on what else to look at?


Thanks.

DorkDisk

The cheapest would be something like a Sugino Impel or Shimano Altus. You wouldn't need to change your BB.

A step up would be a Shimano Deore or SLX. You will need a new BB but the shifting is much improved and the weight loss will be substantial. The "T" touring parts can be ordered but are not necessary IMO. The SLX FC-M670 is very nice and still available

I wouldn't worry too much about matching your current gearing as IMO 28/38/48 is a horrible ratio for these bikes. Considering 48x11 is the same highest gear ratio as pro road racers used BITD, its hard to see how a non pro can use this gear on a heavier bike with suspension, slower tires, and a more upright position

ColonelSanders

Why do you need to replace it?


Perhaps you should peruse the sites of UK retailers who ship to the USA and they have great prices.

travbikeman

I use 48x11 going down hill only. Once on a straight a way, I have to either go down to the 36 on the crank, or a higher gear on the cassette. I'm wondering since Specialized has started switching the gear ranges on their Crosstrails away from such a big gear, if Trek and others will do the same?

rzhunemagu

SLX FC-M670 looks pretty good. Kit already comes with BB? Also noticed that the crank arm length is 175mm vs 170 that I currently have. Assuming that will be OK?

Thanks!

Also how hard is it to replace it? Should I have my LBS do it instead?

rzhunemagu

Was replacing my SPD pedals with a different set and forgot to grease the pedal crank threads before installing. Looks like I've stripped the threads inside the crank

Lesson learned.

csport

I am not an expert, AFAIK, the claim is that the longer cranks can cause injury, but the shorter ones do not, Bicycle Cranks. To remove the crankset from the BB spindle you will need a special tool like this one: Crank Puller for Square Taper Cranks | Park Tool. You will also need wrenches to remove the pedals and the fixing bolts. I am also new, I have started doing the maintenance work myself some time ago and did not have any major problems. If you do not feel like doing it yourself, you can ask the bike shop.

csport

FC-M670 uses external bearings, you need yet another tool to install it. Also, I think FC-M670 is 10 speed; if you have 8 or 9 speed, there may be some problems. You may need to change the front derailleur as well.
I have recently replaced the 48/38/28 square taper crankset with Shimano FC-M590, Shimano Deore M590 9 Speed Triple Chainset | Chain Reaction Cycles. I have also replaced the front derailleur to match the new chainring sizes. This 9-speed crankset works well with my 8 speed drivetrain, I think 8 and 9 speed ones have the same front chainring spacing.

DorkDisk

shorter cranks spin better than longer ones. They do come in other lengths, basically match it to your femur length. If you're tall, go 175 or 177.5. Short, 170 or 172.5. "Standard" crank lengths are 175 for MTB and 170 for road. Longer cranks will lower your seat height and center of gravity a tad but requires more knee bend at the upper stroke. Slightly longer cranks are common now for road, like 172.5. The difference is minuscule and some people notice no difference while others notice immediately.

Crankset removal and installation is relatively easy. The problem is that these two use different toolsets and it makes no sense to buy a crank puller and splined bb tool for a one-time removal and then the HT2 tools for installation. You may want to take it into a shop

Retail packaging will include a BB, while OEM will come in a plastic bag. The vendor will tell you if it is included or not. In any case, HT2 BBs cost about 20 bucks

DorkDisk

Generally cranks are the least picky and most compatible of parts. I run a lot of mismatched drivetrains and currently have two rigs with 10 speed cranks, one 9sp and the other 8sp with no issues

The thing with hybdrids is that they mostly use MTB front derailleurs. If OP has a MTB derailleur, that's already the right radius for the SLX crank. I don't think any manufacturer is speccing a custom cage on these "A level" parts for 48t chainrings.

Given how inexpensive front derailleurs are, and how bad the cheap ones are, it might be a good idea for OP to get at least a Deore level front derailleur and a 10 speed left shifter if you want maximum out-of-the-box compatibility. You will be rewarded with a substantial improvement in front shifting, with noticably less effort, lever throw, and noise

dr1445

+1 on deore fc-m590 from chain reaction but you do need the install tool. i have 2, both on 9 speeds.