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The T-Cycle Sport Over/Under Idler is the second best over/under idler on the market (second only to the Elite Over/Under Idler). With aerospace grade ballistic nylon side plates, tough metal core, durable aluminum cog, tough urethane chainbed, and top of the line ABEC-7 steel bearings, this rugged, workhorse idler will give you years of trouble-free improved drivetrain performance. It's solid, it's quiet, and, quite frankly, it's beautiful. For miles and miles, the Sport Over/Under Idler will prove itself a reliable, quality addition to your recumbent.


1. What's unique about this idler?

Sport Over/Under idlers have a solid metal core surrounded by tough fiberglass reinforced Nylon side plates. The power side chain is supported on a 7075 Aluminum cog and the return side chain runs on a a tough industrial urethane bed. This gives the best of both worlds- a solid metal cog for maximum efficiency and long life on the power side, and a simple, super durable chainbed on the return side. Everything runs on a pair of high quality bearings. It's tough, efficient, and reliable. It's the workhorse idler for any over/under application.

2. How big is the idler?

We make the Sport Over/Under in the 15T size only. It has an outside diameter of 2.75 inches, or 70mm. With 8 or 10mm bearings, it is a drop in replacement for many over/under idlers on a wide range of bikes and trikes. The width is 1.19 inches or 30.3mm, slightly wider than it's Elite cousin.

3. I see it has bolts. Can I take it apart?

Yes, but we do not recommend taking them apart. If they have many thousands of miles on them and you have reason to believe the bearings are finally worn out, please contact us. Since the bearings are pressed into the core, you will need a bearing press if you ever need to remove them. With any kind of reasonable care, the bearings should last tens of thousands of miles, though, and it would be rare to replace them. With a press, even a simple one, it's easy to do.

4. If I ever wear out the cog, can I replace that?

We have only had to do that maybe five or six times, but with tens of thousands of idlers out there, we're proud of how low that number is.  Folks do send us destroyed cogs from time to time, but it's pretty easy to see the ways that improper installation or blunt force trauma has caused their early demise.  If that happens, we would love the opportunity to diagnose your idler and get you back righted again.

5. What about efficiency and noise?

We make exclusively toothed idlers for the power side because they are both quieter and more efficient that way. There are a host of technical reasons for this, but the biggest and most basic one is that chains are designed to be carried by the bushings. It is a nice, big flat area designed for forces to be applied to it. Chains are not meant to be carried on the edges of their sideplates. It just doesn't work as well. Since the core of the idler is all metal, from the chain bushings through to the bearings, there is no sponginess to soak up power. On the return side, the urethane bed is specifically designed with the right durometer to carry the chain quietly without being spongy. Noise is a complicated issue, but we expect you'll find these idlers are quieter than other idlers. The cog is specially shaped to smoothly and repeatably mesh with the chain, and unless the chain is being pulled sideways quite a bit, there will be very little rubbing. We always recommend allowing your power side idler to float side to side with the chain as it shifts. On the return side, the sideplates are tapered and rounded to guide the chain in with as little rubbing as possible. Another common source of noise in drivetrains is insufficient contact on the idler. If there is not enough deflection of the chain at the idler, the chain and the idler don't have a chance to mesh properly. This is true for all types of idlers. You'd think that a chain only lightly touching an idler would be quieter, but because of the complex geometries involved, there is a minimum amount of bend or wrap required to get maximum silence. The amount varies with the diameter of the idler, the larger the idler, the smaller the angle required.

6. What bearings can you get with these idlers?

We make these idlers with 8mm ABEC 7 rated steel bearings, and 10mm, and 3/8 inch, ABEC rated steel bearings. We can make them with 5/8 inch bearings also, but that is for a special version for some Rans idler kits.

7. What's the difference between these idlers and the Elite Series idlers?

The Elite Series idlers have titanium cogs, hybrid ceramic bearings, and completely CNC machined frames. The cog and frame are extensively hollowed out for lightness. They are designed to look as good as they work. The design of the Elite series allows a wider range of bearing sizes to be used.

The Sport Series idlers have 7075 Aluminum cogs, top quality steel bearings, and injection molded fiberglass reinforced Nylon frames. They are designed to be simple, high performance, and tough. The look is much simpler, more businesslike than bling.


  • Available with 8mm, 10mm, and 3/8 inch ID bearings. 5/8 inch bearings are available by special order. The most common bearing size on recumbents is 8mm. Some older bikes and trikes were made with 10mm idler shafts, and only a few bikes were ever made with 3/8" bearings. Some newer European bikes use 12mm bearings, in that case, you would need the Elite version which can take 12mm bearings. Chances are you need 8mm bearings.
  • This idler with the 8mm ABEC 7 bearings is a dropin upgrade for most Bacchetta bikes. 
  • We make the Sport Over/Under in the 15T size only. The outside diameter is 2.75 inches, or 70mm. The width is 1.19 inches or 30.2mm.
  • Weight: 108grams, lighter than any other over/under idler except for its cousin, the T-Cycle Elite Over/Under Idler.
  • The cog is precision machined, but there is a break-in period while the cog and the chain get to know each other. After that, you can expect your idler to last many, many thousands of miles before needing service.
  • We also make matching compatible Power and Return idlers in the 15T size. If what you need is an under/under or over/over setup, you will need separate power and return idlers.
  • In case of damage, all parts are individually replaceable. Contact us for details.
  • We use stainless fasteners because we know you don't want things rusting. We use NyLock nuts on the bolts instead of just running them into the plastic because it's more durable that way and the bolts won't loosen from vibration.
  • The cog is made from 7075 Aluminum for durability. 7075 is a harder, stronger alloy than the more common 6061 and is very abrasion resistant.
  • A third bearing can be added to the return side for the rare applications where that is necessary.
  • Bearing Care: The bearings are shielded, not sealed. Shielded bearings have less rolling resistance because the seal, while super close, doesn't actually rub. True sealed bearings are rare, when people talk about "sealed bearings", they usually actually mean shielded. These are top quality shielded bearings and will last a long time. What kills bearings is solvent, dirt, and water intrusion. As long as you don't spray things on the bearing faces, you will be OK. Regular amounts of dust and dirt getting on the outsides of the bearings won't be a problem, as it's hard for it to get past the shields (the shields really do come *very* close to the bearings). When you clean them, what you want to do is gently wipe dirt off and away from bearings, rather than rub aggressively and push the dirt past the shields. There is no need to lube the bearings, the special grease that's in them is what they need.
  • No maintenance should be required other than occasional cleaning with a paper towel or soft cloth. We recommend keeping solvents and soap and water away from the bearings, they don't need aggressive cleaning and solvents and soaps tend to go after the grease in the bearings. It's water resistant, but solvents and soaps are harder to deal with.
  • You will probably never need to disassemble your idler. Should you ever need to, a 3mm Allen wrench is all you will need.
  • We recommend setting up your idler so it can float side to side with the chain as you shift. If your existing idler mount doesn't allow for this, we offer a variety of upgrade parts to make this possible.
  • This idler is a direct replacement for the over/under idlers on most bikes and trikes with over/under idlers. 8mm is the most common bearing size. These idlers can also be ordered with 10mm, 3/8 inch, and 5/8 inch bearings.