Unstable tight turns with R&M Supercharger?

[DanRichman]

Is anyone else experiencing unstable turns on the R&M Supercharger? Maybe it's me, though I've ridden a road bike for years.

When I try to make a tight turn on this bike, I feel like I'm going to fall over (inward, in the direction of the turn). And I nearly have, a number of times.

It's not wobble or shakiness. There's nothing mechanically amiss. If anything, it's a matter of design.

I have to make very wide turns (sometimes running out of room on narrow roads or trails) in order to feel stable. Often I'll put my inside foot down to prevent a fall.

Any thoughts welcome

 

[michael mitchell]

Probably due to the increased weight and higher center of gravity, compared to a road bike. Both my ebikes definitely handle tight turns different than my road bike does.

 

[Over50]

I don't know if perhaps wheelbase has anything to do with it. My Haibike and my Riese and Muller have the same tires. The Haibike is a smaller frame and shorter wheelbase. It also has only one battery vs the dual battery Riese and Muller (one battery on top tube). I don't feel unstable on the Riese and Muller but the Haibike definitely feels more nimble to me and I can achieve tighter, faster turns. I slow down a bit more for tight turns on the Riese and Muller. It isn't a huge difference but to me seems a bit noticeable.

 

[dblhelix]

Is anyone else experiencing unstable turns on the R&M Supercharger? Maybe it's me, though I've ridden a road bike for years.

When I try to make a tight turn on this bike, I feel like I'm going to fall over (inward, in the direction of the turn). And I nearly have, a number of times.

It's not wobble or shakiness. There's nothing mechanically amiss. If anything, it's a matter of design.

I have to make very wide turns (sometimes running out of room on narrow roads or trails) in order to feel stable. Often I'll put my inside foot down to prevent a fall.

Any thoughts welcome

I’ve noticed the same with the Charger. A couple of times I have stopped and turned the bike myself by picking up the frame. Turning right seems a tad more restrictive.

 

[rannyv]

Glad I got the R&M Roadster instead of the Charger. I tried the Charger and it felt too large, kind of clumsy and heavy.

 

[Deleted member 18083]

Dan ...

• Wheelbase
  Supercharger : 113, 116, 118 cm // Roadster : 108, 111, 115 cm // My Road Bike : 98 cm
• Trail
  Supercharger : 92 mm // Roadster : 83 mm // My Road Bike : 62 mm

As these numbers increase, manoeuvrability (Roadster better) is sacrificed for stability (Supercharger better). I've added the figures for my road bike which has a "relaxed" (meaning comfortable non-racing) design.

I do realise that I've not explained why these numbers affect stability; haven't even defined what "trail" is. Keep it simple.

An easy solution to toppling when turning around on a trail is to install a dropper post which will allow you to place both feet on the ground. Unfortunately, the choice will be between a dropper post and a suspension post.
... David

 

[rannyv]

I don't imagine that battery in the top tube and 2X battery help handling. The range is nice if you need it, but if you don't, it's just excess weight.

 

[Mr. Coffee]

The Charger and Supercharger have a really long wheelbase. In most cases that makes them really stable (you can hit insane speeds on steep fast downhills and feel like you are on rails) and is nice if you are carrying a bunch of stuff.

One mountain biking friend opined that e-mtbs tend to have long chainstays to offset the extra torque of the motor. But the charger and supercharger take that to pretty wild extremes.

The downside is that they lose a lot of maneuverability and tend to feel ponderous at low speeds and in tight turns. One more reason to argue that in spite of their hardtail-like design they aren't really mountain bikes.

 

[dblhelix]

Dan ...

• Wheelbase
  Supercharger : 113, 116, 118 cm // Roadster : 108, 111, 115 cm // My Road Bike : 98 cm
• Trail
  Supercharger : 92 mm // Roadster : 83 mm // My Road Bike : 62 mm

... David

David, where is the tech data on the models posted at RM’s site? Thnx.

 

[Tiny]

The R&M Supercharger has two batteries, is a very heavy bike with a high center of gravity. My R&M Nevo is a bit sensitive or twitchy in steering. It requires both hands for good control. I like it this way since I am able to dodge imperfections in the roadway quickly.

 

[dblhelix]

The R&M Supercharger has two batteries, is a very heavy bike with a high center of gravity. My R&M Nevo is a bit sensitive or twitchy in steering. It requires both hands for good control. I like it this way since I am able to dodge imperfections in the roadway quickly.

Perhaps, but I have strapped weight and changed GG while bikepacking with non-e bikes w/o major issue. In my case, the problem seems partially to be partially from a restricted turning radius. It’s something I’ve been meaning to look into, so I’m glad Dan brought this up.

Dan, when you turn your handlebars l/r, what kind of angle can you make, assuming that straight ahead is zero?

 

[LVSW]

I've been riding my supercharger for about a month now. My usual route is pretty wide open so I probably don't go thru as many tight spots but for what it's worth I've never felt like I was in any danger of going down.

 

[Deleted member 18083]

David, where is the tech data on the models posted at RM’s site?

Double Helix ...
The tech data for each R&M model is listed in dropdown tables for "Specifications" and "Frame Geometries". You'll need to click through to an exact model - the page that displays the price. Let's use Dan's Supercharger GX Rohloff HS as an example...

To find your way to tech data...

1. Start with the R&M Models web page and from it...
2. Click the link to the Supercharger web page and from that...
3. Click Supercharger GX Rohloff HS...
4. Scroll down to "Frame Geometries" and click the down-arrow to expand the table.

... David

 

[Deleted member 18083]

"Trail" refers to how far the tyre's contact point with the road trails behind the steerer tube axis's point of contact with the road (blue line).

For road bikes trail typically ranges from 50 mm (agile) to 63 mm (stable) with 57 mm widely regarded as the sweet spot.

Contributing to the Supercharger's hyper-stable trail of 92 mm is a "shallow" head tube angle (69 degrees) which brings the handlebars back towards the rider and pushes the axle forward.

 

[dblhelix]

I've been riding my supercharger for about a month now. My usual route is pretty wide open so I probably don't go thru as many tight spots but for what it's worth I've never felt like I was in any danger of going down.

I’ve never felt like I’m going down either, but that’s because the steering turning radius prevents me from making the turn so I’m grabbing the frame and using my feet to reposition the bike. The restricted steering has more of a motorcycle than bike feel to me. And I stand corrected - it is turning left that is slightly more restricted.

It may be the case that it’s intentionally restrictive. Different people with different heights/weights may be experiencing different effects at low speeds where CG matters.

 

[Feliz]

I'm always surprised how little attention people pay to bike geometry before purchasing, most folks I know are more concerned about the motor's power than about rake and trail etc.....that's a mistake.

 

[dblhelix]

I'm always surprised how little attention people pay to bike geometry before purchasing, most folks I know are more concerned about the motor's power than about rake and trail etc.....that's a mistake.

For real? Are you talking about the reviews?

I don’t think “people”expect to have to make a billion point turn with their “sporty” bike. Opportunities for testing tend to be limited. I wasn’t offered a “keep it for a day” type arrangement, although one take-home from this experience has been not to buy one of these bikes again without ample opportunity to test.

 

[Tiny]

Trail can vary as a result of suspension activates, in response to braking for example. As telescopic forks compress due to load transfer during braking, especially braking of the front wheel, the trail and the wheelbase both decrease, causing a decrease in stability. Use caution in braking the front wheel. Only on the straight and level.

 

[Feliz]

For real? Are you talking about the reviews?

I don’t think “people”expect to have to make a billion point turn with their “sporty” bike. Opportunities for testing tend to be limited. I wasn’t offered a “keep it for a day” type arrangement, although one take-home from this experience has been not to buy one of these bikes again without ample opportunity to test.

That was my point, an experienced rider familiar with how a bike's geometry affects handling can pretty much predict how a bike will handle from looking at a bikes specs.

 

[Mr. Coffee]

On a related note, has anyone noticed a high-speed wobble on the Charger or Supercharger?

From a design standpoint, the long wheelbase, long trail, and stiff aluminum frame all tend to produce at least a modest shimmy at high speeds. Depending on the road surface, I have noticed a little wobble as low as 50kph, and sometimes a fairly dramatic wobble at 70-75kph.

I've found three things that help mitigate (or eliminate) said wobble:

• Unlock the suspension fork. This nearly always does the job.
• Drop the seat.
• Press one or both of your thighs against the top tube. This is the best bet if you are flying down a hill and find yourself in a wobble and are afraid to reach down and unlock the fork.