DMR Simple Tension Seeker

I have used several methods to tension chains on single-speed bicycles and they all have problems. This one, though, worked with no issues or fiddly adjustments. There is no spring--you set the tension by pushing it up or down onto the chain and tightening up the bolts. The roller finds its alignment with the chain after a few spins of the cranks. An argument could be made that a spring system adjusts as the chain stretches; however, if that happens it is simple to readjust the tension (5mm Allen key required) and ride on. I image this would only happen once during the life of the chain. I installed it in about 10 minutes and used the rest of my free time to go on a bike ride. If it develops problems, I'll update this review.

I wanted to use this on a single speed (i.e. bike with a single gear ring - aka single front sprocket) and a single rear sprocket. This item seems to be designed for use with a multi speed cassette in the back as the chainline was too far outboard for a single rear cog on the hub. In order to get it to align I had to bend the frame of the item and as such render it beyond return. It is going to be donated to a charity bike repair shop. It is a very well made item and has great looks and I am disappointed I had to learn about not being able to use this ... the hard way. Would I recommend it? Absolutely: it is a quality product but just not made for what I needed.

First thing pulley wheel has a quarter inch play left or right. Even if you have a perfectly straight chain line & spaced rear cog with chain tensioner, chain will still jump off at some point. This can be fix with some nylon spacers on pulley wheel axel to maintain its position. Second issue this can not be fixed, chain tensioner bolts on clockwise. When pedaling forward chain puts tension on chain tensioner counter clockwise, ride few times & chain will be loose. I've watch multiple youtube videos on this item & read the reviews, which is why I purchased chain tensioner & it looks cool. If you've been down this rabbit hole you would no this was being installed with just the one bolt multiple sources reddit youtube forums, the chain tensioner has a second bolt that can be used with a rear wheel quick release axel. Even with second bolt on quick release axel it still becomes loose because it is slotted & it slides out of position because of chain tension is in opposite direction, no matter how hard you tighten bolts. I've tried this on two bikes my single speed free wheel quick release hub with both bolts & ebike converted to single speed. I'm past the return date because I had to order an M10x1.0 bolt from china because included bolt was way too short & had to add 10mm axel spacer in order to make pulley wheel line up with rear cog spacing. I tried lock washer & star tooth, other chain tensioner either have a spring or adjustment bolt that would stop rotation on derailleur hanger. You would have to adjust tensioner after every ride, how is this not mention in any other reviews anywhere here reddit youtube bike forums. Everyone online is telling you to buy this chain tensioner its the best.

Picked up a single speed converted mtn bike second hand and it had a crappy cheap tensioner that caused the chain to skip anytime you pedaled! Got this tensioner and ZERO skipping. Feels like a high quality product. I also like that the bearings are a standard skateboard style so they could be easily replaced if they wear out. Best tensioner hands down.

First thing I noticed is this tensioner felt solid. I converted a vintage mountain bike to single speed and needed to take up the chain slack since the frame wasn’t horizontal drop outs. Worked out perfectly paired with a single speed cog and spacer kit. There is a slight negative….no instructions….but it was easy to “figure out”. Happy to be ripping around again. Enjoy the ride!

Most importantly; THIS DOES NOT WORK WITH 1/8 CHAIN. I stuck mine on a lathe and opened it up a bit and I love it. Silent, holds tension very well, impervious to dirt and sticks.Rode with a friend who has a spring tensioner, got into some nasty mud he was skipping constantly on climbs while I was fine. Another complaint though. I had to put this thing in a vise and make some adjustments in order to line up the chain. It wouldn't reach in towards the tire enough to line up. Thats the only reason I couldn't give it a 5 star.

It is a great design with 2 sturdy connection points and no need for springs or extra moving parts. It makes installation simple and clean looking. Great for an ebike (or any) as it can push the chain up to increase cog contact instead of down for less.

Updated review: Going on two years and 4K miles the DMR keeps on going. The only drawback is that it must be unbolted from the mount (2 bolts) for rear wheel removal since the mount comes off with the wheel. Also, since most SS conversions will have uneven chain slack, it must be adjusted where slack is smallest to avoid excess chain tightness. Once adjusted and tightened it stays put and maintains proper slack until chain wears.