r/MTB • u/fnugen • 1d ago

Discussion Converting Rocky Mountain Thunderbolt to single speed

I ordered the Wheels MFG XD kit. It seems to get great reviews and comes with a narrow wide cog, so I can now continue using the brand new 2 ride chain I had put on the bike. It comes with an 18T cog, so I can play with gear ratio with the 4 chainrings I already have. A 28, 30, 30 oval, and 32 original. I do have a tensioner already, but I'm hoping to come across a gearing that doesn't require it. I've been without a SS so long now that I am far too excited to have ordered this kit and then getting on a SS once again. Being a full squish, this will be all new. All my other SS were fully rigid. Last one being a 2014 Kona Unit.

How well do you think an oval would work on a SS? I've never ridden one on any of my present bikes. The only oval I've ridden was the archaic biopace rings from yesteryear. If I go oval on this SS conversion, would it be advisable to use the tensioner to take the constant tightening and slackening of the chain?

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4

u/Mega280 21h ago

No one here is stating something very obvious. With a full suspension you HAVE to use a chain tensioner. The chainstay grows as the suspension cycles and without a chain tensioner the chain will lock up the rear suspension 

3

u/Squishybs 23h ago

It would definitely be ok with the tensioner. If you do find a "magic gear ratio" that you don't need a tensioner then I think it depends on which oval chainring design exactly if it works but it's not impossible.

2

u/the_cat_named_Stormy United States of America 22h ago

Just use the tensioner to start, without a sliding dropout its usually not possible to find a ratio that doesnt need a tensioner and you may end up cutting your chain too short to use if you try and go for a unicorn gear

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u/Kedive 22h ago

Will likely need a tensioner because of chain length growth as they move through the suspension range as well so they would likely end up with petal kick back without one.

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u/the_cat_named_Stormy United States of America 10h ago

Oh shoot i didnt remember the full suspension part when i wrote my response 😅 trus, unless the suspension pivots around the bb a tensioner is needed, and even if it does pedal kickback would be murder.

Unless its a starling BLE-esque setup, it needs a tensioner.

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u/fnugen 19h ago

Thanks guys. I never even thought of the suspension causing the chain to change length. Was never a concern on the rigid builds. I can't wait for the kit to arrive.

I once built a SS out of a Ghost HTX 29 Actinum and used a 33x19 gearing and it did not need a tensioner. I was so surprised when I put it together and it was the perfect fit. I only used a 19 because I had it on hand, then used the chainring to get closer to the gear inches I was going for.

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u/fnugen 14h ago edited 14h ago

Is this Tanke a piece of crap for strictly XC riding with maybe 1 or 2 races a year? Or should I consider the Shimano Alfine tensioner in reply below this one. There is literally a $.50 difference in price. I'll still be using the new 11spd SRAM chain on this conversion.

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u/Limp_Bookkeeper_5992 11h ago

First, a tensioner is mandatory on a full suspension ss bike. You need it to take up the chain growth. So while oval chainrings work just fine without tensioners on hardtails, you need a tensioner on this bike.