Downhill Slope

EBEB

I have a variable height motorbike stand that I was going to put under the front wheel and am about to build a fixed box for the rear wheel to sit on, so that I can simulate downhill as well as uphill.

Before I cut the wood to make the box I have been trying to decide how steep a gradient downhill I will want to be able to simulate, but can’t decide and I can find pretty little data to help.

At what gradient do people think I should want to be able to cycle downhill at? With a 53x11 and a maximum comfortable cadence of 125 I get a max of 75 kph. Much above that and I think I’d have to freewheel, so there is little point simulating really steep declines.

I was thinking maybe 7.5%…

The maximum for the motorbike stand is high, so I don’t think that should be a limiter. The turbo is going to be strapped to the box, which will have weights in it, so stability shouldn’t be a limiter either. The only real limiter that is in effect here is pointlessness.

Has anyone tried this? Does anyone have a different % suggestion?

imposter2.0

FFS..

fenix

Seriously ?

kingstongraham

EBEB wrote:

The only real limiter that is in effect here is pointlessness.

Nail hit there.

jgsi

As this forum has gone completely downhill in its content over the last few years and has become a feeding ground for idiotic troll posts and responses, it is quite appropriate.
Best thing Bike Radar is close it down and start again... it has become a joke forum.

kingstongraham

JGSI wrote:

As this forum has gone completely downhill in its content over the last few years and has become a feeding ground for idiotic troll posts and responses, it is quite appropriate.
Best thing Bike Radar is close it down and start again... it has become a joke forum.

I like it, that's why I'm here. You?

cougie

JGSI you can just leave if you don't like it ?

Most posts are sensible and it would be incredibly dull if they all were.

imafatman

This is dumb.

me-109

I'll play.

Have you ensured you have enough headroom when seated on the bike sat on top of the trainer on top of the box?

I reckon more like 10-15% so you can spin up and then practice your range of tuck positions as the trainer spins down.

MiddleRinger

EBEB wrote:

The only real limiter that is in effect here is pointlessness.

And since when has that ever stopped people doing things?

Start with 10% and work from there. Do it. Post videos.

rdt

EBEB wrote:

At what gradient do people think I should want to be able to cycle downhill at? With a 53x11 and a maximum comfortable cadence of 125 I get a max of 75 kph. Much above that and I think I’d have to freewheel, so there is little point simulating really steep declines.

I was thinking maybe 7.5%…

For added realism - albeit requiring a large budget - add in a Tacx Neo for its downhill drive, but be aware that -5% gradients are the maximum simulated.

Also consider extreme high velocity fans to simulate wind feel, together with a system for feeding large flies and bees into the airflow. Glasses should be worn if that's what you'd do outside.

For the even less budget-conscious, consider running a Tacx Magnum in reverse with your bike pointed downhill, although you'd need to boost the motor drive somewhat to simulate the descending speeds being discussed (may void warranty)

EBEB

Well thanks, that was helpful. Glad to see so many grown ups inhabiting this forum.

cougie

Why do you want to do this ?

markhewitt1978

Yeah; it's completely pointless, so pointless that Wahoo have a product which does exactly this - they probably thought it was pointless too.

markhewitt1978

EBEB wrote:

I have a variable height motorbike stand that I was going to put under the front wheel and am about to build a fixed box for the rear wheel to sit on, so that I can simulate downhill as well as uphill.

Before I cut the wood to make the box I have been trying to decide how steep a gradient downhill I will want to be able to simulate, but can’t decide and I can find pretty little data to help.

At what gradient do people think I should want to be able to cycle downhill at? With a 53x11 and a maximum comfortable cadence of 125 I get a max of 75 kph. Much above that and I think I’d have to freewheel, so there is little point simulating really steep declines.

I was thinking maybe 7.5%…

The maximum for the motorbike stand is high, so I don’t think that should be a limiter. The turbo is going to be strapped to the box, which will have weights in it, so stability shouldn’t be a limiter either. The only real limiter that is in effect here is pointlessness.

Has anyone tried this? Does anyone have a different % suggestion?

To actually answer the question. The Wahoo Kickr Climb does -5% to +20%, so I would aim for something in that region. The point being that while you do want to simulate going down hill to a degree it's the climbing position that you want to be focused on. So in that regard if you are doing away with the front wheel then there shouldn't be a massive need to raise the turbo to compensate.

There are other issues of course, namely can the axle on your turbo rotate freely? As if it can't you're going to damage your frame.

StillGoing

markhewitt1978 wrote:

Yeah; it's completely pointless, so pointless that Wahoo have a product which does exactly this - they probably thought it was pointless too.

Wahoo's device is for uphill, not simulating a downhill. The whole concept is pointless and verging on idiotic.

markhewitt1978

philthy3 wrote:

markhewitt1978 wrote:

Yeah; it's completely pointless, so pointless that Wahoo have a product which does exactly this - they probably thought it was pointless too.

Wahoo's device is for uphill, not simulating a downhill. The whole concept is pointless and verging on idiotic.

The Wahoo device simulates both up and down hill.

StillGoing

markhewitt1978 wrote:

philthy3 wrote:

markhewitt1978 wrote:

Yeah; it's completely pointless, so pointless that Wahoo have a product which does exactly this - they probably thought it was pointless too.

Wahoo's device is for uphill, not simulating a downhill. The whole concept is pointless and verging on idiotic.

The Wahoo device simulates both up and down hill.

Accepted, but it isn't mounting a turbo on a box with the front wheel off to ride just downhill. I fail to see what the OP's concept actually achieves other than becoming a contestant for a Darwin award when it all collapses. Sit on a turbo with little or no resistance if you just want to pedal fast as pointing the bike downhill will make no difference at all without gravity being involved. On a static trainer, gravity obviously isn't going to be having any effect.

chris_bass

I don't want to speak on the OP's behalf but i'd assume it is to work on spinning out in the correct position for downhill riding?

where the weight and pressure points are is quite different on a steep downhill slope than it is on the flat and different again uphill, I think that is the reason the kickr climb exists.

Not something I'd spend much time on developing or seeking out but the world would be a boring place if we were all the same.

StillGoing

Chris Bass wrote:

I don't want to speak on the OP's behalf but i'd assume it is to work on spinning out in the correct position for downhill riding?

where the weight and pressure points are is quite different on a steep downhill slope than it is on the flat and different again uphill, I think that is the reason the kickr climb exists.

Not something I'd spend much time on developing or seeking out but the world would be a boring place if we were all the same.

OK the pull of gravity on the arms is going to be minimal unless the OP is wanting to practice going off of a precipice. If they just want to practice spinning out, that can be done by using the inner ring and low gearing.

imposter2.0

'Practicing spinning out in the correct position' is not actually a thing though..

chris_bass

Hey, I never said I'd be doing it but just trying to help the OP out a bit!