RST Dropper Post & Inverted Fork

Words Andrew Major
Photos Fergs
Date Oct 4, 2016

RST has been kicking out budget oriented OE suspension products for kids, commuters, and basic mountain bikes for years. Building from those experiences, they have some interesting new products in the form of the RST dropper post and their inverted single crown fork.

RST Dropper Post

Mike Dunn from RST cut right to the chase in introducing their new dropper post: “What are the two main problems riders have with dropper posts? They blow up and that side-to-side play.” With their 30.9 and 31.6 x 120mm dropper post, RST has set out to resolve both of those issues.

The projected price for the post is $290 (USD). That includes two different remotes.

RST Dropper Post

RST’s dropper post is not light weight. A big part of that is 32x needle bearings that prevent any twisting of the post. The internal cartridge is designed with durability in mind, is easy to change, and a replacement will run you $19.95 USD.

Needle Bearings

The cutaway post on hand immediately had me thinking Cannondale Lefty but the actual parts are right out of a Headshock-like commuter fork that RST has been manufacturing for years. The square faces of the post’s internal shaft are captured on all four sides and roll on the needle bearings. No worn brass key-ways resulting in slop here.

The projected weight of the post is 680 grams. Yes, it’s heavy. If it meets its claims regarding reliability I don’t know if I’d care about the extra hundred grams or so compared to other posts.

RST Dropper Post

The RST Dropper will be available with both a fixed external cable or stealth routing. It comes stock with both a shifter compatible remote and an under the bar remote with very nice shifter-like ergonomics.

The $19.95 Replacement Cartridge

Yes. Have to bold that. If the cartridge in the RST dropper post blows up you can easily swap it out for another self-contained cartridge. You don’t even have to remove the post from your bike to make the swap. Replacement cost? $19.95.

That covers replacement cost but Mike also claims the RST dropper post has the most reliable guts in the industry. RST purchased the drop-in internals from a company that makes lift cylinders for Toyota.

The post has non-adjustable return speed à la Crankbrothers Highline. I haven’t yet ridden one so I can’t comment on how much of a ball buster it can be.

RST Dropper Post

The shifter-like ergonomics of RST’s under the bar remote are very good. I would love to see a longer remote lever for increased leverage and a lighter feel. Here is a shot of the stealth version of the post.

RST Inverted Suspension Fork

RST’s inverted suspension fork is 29″ and 650b+ compatible. It has 80mm to 140mm of internally adjustable travel. The fork offset is a pretty standard 51mm. It has a simple air system with a self-balancing air negative spring. There’s also some cheeky axle tech going on. All for a projected price under $1000 (USD).

There are no fork guards available at the moment. Mike says they’ve had one stanchion scratched out of 50x test forks in the wild and it was when he threw his bike down to do something chivalrous in the Whistler Bike Park. That said, RST is working on some optional stanchion protection.

RST Inverted Fork

One piece magnesium upper. Adjustable low-speed compression and rebound. Super simple air system. Sweet looking USD fork from RST.

RST Air System

No stanchion dimple. No check ball. Just two Schraeder valves that both open simultaneously when you start pumping. It is definitely the simplest self-balancing negative air spring system I’ve seen. It would not be possible to increase the progressiveness of the air spring using oil, however it should be relatively simple to take up some volume in the main chamber using volume spacers.

In the same vein as the RST dropper post, this is an effort to make a simple, high-value product that also functions well.

ib2016d4-rst-air-chamber-valve

Simple to rebuild is the name of the game with RST’s products. The air system uses two inline Schraeder valves to fill both the positive and self-balancing negative air chambers at the same time. Second Schraeder valve marked with a red arrow.

Locking Axle

The RST fork does not use a key-way design or needle bearings, so how do they keep it from riding like a noodle? The one piece uppers help but the main feature here is a locking axle. Which is cheeky because somebody else has a patent on exactly that for US forks.

The workaround is to have the axle lock into one dropout, not both. The axle receiver locks into the other dropout to prevent twisting.

RST Inverted Fork

The axle locks into the damper side dropout.

RST Inverted Fork

The axle receiver locks into the disk side dropout.

Both the RST dropper post and inverted fork are close to production. More options are always better and I’ll be harassing Mike for an opportunity to try both products in the real world.


Anyone else remember the Mozo Pro XL?

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Comments

poo-stance
0
Poo Stance  - Oct. 8, 2016, 10:35 p.m.

The Lefty needs to come out in a dual stanchion design! 140-180mm travel for 29era

Reply

brad-sedola
0
Brad Sedola  - Oct. 5, 2016, 2:49 p.m.

What's the clearance for 29″ tires? Could it handle a 29+? 3″ rubber? Straight legs I would think it could clear between the fork legs. Crown clearance would likely be the only restriction, but could likely be managed with spacers similar to the ol' Maverick forks.

Reply

drewm
0
DrewM  - Oct. 5, 2016, 4:26 p.m.

Hi Brad, I'll endeavour to get you an axle to arch measurement at bottom out. I've seen 29″ plus done with all manner of forks including Fox's standard 34 29″. Just a matter of adding travel limiters (not travel reducers) as you note. Maverick and Manitou Dorado are two prime inverted examples that work this way and it shouldn't be a problem with RST.

Just a matter of how much travel you get for the axle to crown height.

Reply

moity
0
moity  - Oct. 5, 2016, 12:26 a.m.

Dropper: 120mm travel, overweight, and not exactly cheap… onto a winner there. Oh and if it blows up just throw the guts away and drop in a new cartridge, which I'm sure will be readily available.

Don't mean to sound so negative but why are these so hard to make, and to allow them to be serviced rather than throwing parts away?

Reply

drewm
0
DrewM  - Oct. 5, 2016, 12:58 a.m.

Overweight compared to what? No dropper posts are particularly lightweight and yes this is a bit heavier than many. The 32x needle bearings and interface vs. two brass keyway bushings is going to account for a lot of the difference. If it can deliver easy maintenance and slop-free performance it will be worth the weight penalty for a lot of riders.

120mm / 125mm travel seems to be the starting point for new dropper posts: Crank Brothers, Shimano, X-Fusion, RST, etc. Run before you walk. My guess is that all these companies are working on longer options as there is a vocal amount of demand for posts delivering 150mm, 170mm, 200mm, etc.

My guess that the very vocal minority aside the bulk of riders looking for a dropper post are still well served by something in the 125mm range.

Why aren't the cartridges rebuildable? Likely its to do with cost and trying to keep the costs down for competitive initial pricing. Some are more completely serviceable (Thomson, Fox) but have to be shipped out to be done. Some are fully rebuildable at a dealer (or at home if you have the stills) but the rebuild costs are very expensive (Reverb). A full rebuildable cartridge may add to the initial purchase price to the extent that the product wouldn't be sellable.

In the case of the RST, I will hopefully have the opportunity to get one apart soon to better talk about the guts.

Thanks for reading,

Reply

bart
0
bart  - Oct. 5, 2016, 8:44 a.m.

Should see RST at a Canadian distributor soon….so parts should be available fairly easily attainable. Also when you build a product to be non-serviceable you can generally make it to tighter tolerances.because you don't need to engineer pulling it apart into the equation.. take Shimano master cylinders Vs HFX 9's…. there is a reason brake manufacturers tend to not make these re- buildable anymore.

Reply

drewm
0
DrewM  - Oct. 5, 2016, 8:46 a.m.

Great point; thanks Bart.

Interesting aside that the mineral oil masters are not rebuildable (Shimano / Magura) but DOT ones are (SRAM, Hope, Formula). Maybe taking into account tight tolerances vs. a need for serviceability?

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