As shelter-in-place continues in Northern California, at GearGuide we continue to tinker. We started with a small update to the drivetrain of a Marin hardtail, a new dropper post and the like. But those additions didn’t go far enough.
What good is a new front chainring without a corresponding rear cassette? How can a derailleur designed for a maximum 36-tooth rear sprocket handle 42? And heck, why not upgrade some contact points while we’re at it?
We tackled these additional changes in much the same way as before. We hit a range of retailers including Amazon, REI and our local bike shop. And when those failed us, we hit HomeDepot for a few bits. Here’s the rundown.
After our last round of updates, we took our trusty Marin to the Tassajara Ridge, a long and steep incline that’s been a great test of uphill prowess. Without the lower gears of the old 3x drivetrain we struggled and resorted to finishing the climb on foot. Time for a new rear cassette.
We checked the forums and our various retailers and ultimately decided on the SunRace CSM980 11-40 tooth nine-speed cassette. The range looked right to us and the 40T low gear was just about the limit of what we could handle with the original Shimano MD-592 long-cage derailleur still in use on the Marin.
Installation was easy, helped by a chain whip and sprocket remover. We replaced the chain at the same time with the new KMC 9x mentioned in the previous article.
All the creaks and groans of the old drive train disappear with this update. Shifts were more positive through all but the lowest gear which didn’t quite have enough clearance with the original b-screw. Onto the next update.
Find the SunRace CSM980 on Amazon. About $35. And by the way, the new cassette made all the difference in the climb. No more foot stomping to the top. It’s still a tough slog but all from the saddle now.
MTB B-Screw Replacement
A b-screw or body-angle screw is employed on most derailleurs as a way of adjusting the spacing of the guide pulley to the cogs. There’s a great article on the Park Tool website discussing this and other derailleur adjustments.
The Shimano MD-592 comes with a b-screw that’s approximately 15mm in length allowing for a specified maximum rear sprocket of 36T. Pushing to 40T is possible but the original b-screw doesn’t quite allow for the recommended five to six millimeter distance between the derailleur pulley and cog on the new SunRace cassette.
Luckily, Wolf Tooth makes a bike-specific 25mm version that’s available from several retailers including Amazon and Jenson USA. Not being willing to wait, however, we contacted several local bike shops and found nothing in their inventories. One of the mechanics directed me to HomeDepot telling me that Shimano uses standard M4 machine screws.
Indeed my local store had them in their specialty parts bin in sizes ranging up to 25 mm. We picked up 20 mm, 22 mm and 25 mm varieties for less than $4 (some b-screw kits can cost upwards of $15). Quite the bargain, but would they fit? The answer was “yes.” The 22 mm version worked perfectly and shifted our Shimano derailleur enough to get the recommended clearance.
Find the M4 screws at Home Depot.
While we were poking around for new gear, we decided to update a few of the all important contact points including the saddle. Now saddles represent one of those categories where you can spend hundreds of dollars on exotic materials and fancy construction. But we’re budget minded and found a nice option at REI.
The Bontrager Sport Bike Saddle hits around $35, so a definite bargain. It’s steel not titanium, of course. And Bontrager constructs the seat from synthetic materials. We found it very comfortable and a nice upgrade.
Find the Bontrager Sport Saddle at REI.
After a few rides with the new setup, we’re faster and more nimble. But we also notice a bit more chain slap given our newfound speed (and potentially the lack of a clutch-style derailleur). The new KMC definitely knocked some paint off the drive-side chainstay which isn’t good. So we started looking for some options to protect that part of the Marin.
We found plenty as you’d expect. Everything from neoprene sleeves to mock carbon fiber stickers. Prices range up to $30. In keeping with our budget-build ethos, we dug through the garage gear bin instead.
In the bin, we found awesome heavy-duty PVC tape. It’s designed to be used as pipe wrap. It’s adhesive backed, two-inches wide and 20 mil thick. Plenty tough to handle chain slap. At less than $6 for 50 feet, it’s another huge bargain. We finished the ends with a bit of electrical tape and hit the trail for close to nothing. Scuff off the writing if you want to cleaner look.
Find it on Amazon or at Home Depot.