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90 % I bike off road, but easy and lazy, but 2 3 times a year I go seriously up hills I mean Ventoux and that kind of stuff. I would like then to use tires that are somewhat more effective. Since I want the Bad Boy per se 2 questions,

  1. will I have problems going down hill at speed
  2. what size of tire is the most effective

thanks Henk

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  • Henk, I think a little more information on what kind of riding you do normally would help, especially in relation to the tyres. Are you looking for something with the most grip? or with the lowest rolling resistance? or the best puncture resistance? In relation to going down hill at speed, if we look from a danger perspective I think knowing what brakes you have, and your weight would matter most. – Henry Jan 21 '16 at 18:19
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You've really got a few things going here.

For going up hills easier, you have 2 aspects for a given bike:

  • Bike geometry and bike fit: If the geometry of the bike is not good for climbing and/or you're poorly fit to it, its going to be harder than necessary. So play around with adjusting your saddle height + position + stem + handlebars.
  • Gearing: For going up a hill, you want a low gear (big cog in the back, smaller chainrings in the front). Your tire size does play into this a bit, but its secondary (bigger tires = higher gearing). You can use something like this to calculate gearing.

So, if you want to make it easier for a given bike to go up a hill, fit a cassette/freewheel with bigger gears, and use smaller chainrings in the front. Note that lower gearing means that your top speed won't be that high.

When descending a hill, you also have two things: - Bike geometry and bike fit: The position of you on the bike and the geometry will determine the stability and control you have when descending. - Brakes: Brakes are the way you'll primarily stop. If its a big descent, you have to be careful not to overheat the brakes/rims, so you need to choose appropriate brakes (this includes pads, calipers, etc.) that provide the right level of braking for the weather/terrain and modulate them appropriately (e.g. if you go down a long hill and just hold the brake partially on, you may boil your brake fluid on a hydraulic brake, just like you would on a car).

Your gearing won't necessarily matter all that much on a bike with a freewheeling mechanism, since you'll either have a gear that you can accelerate with or you'll be freewheeling (and if you want to accelerate, you'll want to add combinations of higher gears (large chainring, small cog in the back)).

Tires: For road use (on a clean/wet road), you want smooth tires. Knobbies increase resistance on a road, plus when cornering at high speed can flex and lead to wiping out. Also set your tire pressures correctly (this is important for comfort and control). Off-road or snow will favor some form of knobbies. As for tire sizing, note that it does affect the standover height a bit, but this is a personal preference determined by how much you weigh, how much comfort you want (bigger tires at lower pressure are more comfortable), how well the tire stands up to cornering (which is determined by how flexible the tire is as well as the pressures its run and its size -- a big low pressure tire may flop off at a high speed corner when a thin high pressure tire wouldn't), puncture protection, rolling resistance at a given inflation pressure among other things. Note that you don't want to run a very wide tire on a very narrow rim and vice versa due to the tire coming off or hazards damaging the rim.

Unless you're riding on a road and you have knobby tires, I'd probably start with finding appropriate gearing (by swapping freewheels/cassettes so you have a big enough big cogs for the uphills and small enough small cogs for the downhills) and making sure brakes are up to snuff (probably starting with having good brake pads and the brakes are in adjustment). If you are riding on a road and have knobby tires, buy some slicks.

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Do you mean Mt Ventoux in France, frequently part of the the TDF and classed as a real bastard of a climb?

Looking at segments like https://www.strava.com/segments/993229 even the top riders struggle to get 14 km/h I'd be grinding away at 4 to 5 km/h.

Ventoux, Bedouin route From http://www.veloventoux.com/?c=montVentoux where there's analysis of all three approaches.

Any geared bike can climb this, provided you can push the pedals - that is, the only thing that will stop you is running out of leg muscle in your bottom gear.

Since you imply you've done this before, I guess you're asking how to do it better.

Tyre choice - Assuming you're not changing rim size, then you're asking about width and tread. I'd recommend the thinnest tyre that your rims will support. This may be a commuter tyre with a 1.25" width and as smooth a tread as possible. Knobblies are less suitable. Pressure should be at the upper end of the supported range for your tyre.

Descending at speed - I have higher peak and average speeds on my MTB than I get on my road bike. So the wider handlebars of a MTB will give more stability and confidence.

Braking technique helps - you need to corner cleanly and stay well to the correct side of the road. Brake hard on the front with your bum backwards to wash off speed, then lean into the corners, and power on to exit them. Keep the eyes aimed at where you want to go, not the road in front of you. Do not ride the brakes - you'll get better effect from 2 seconds hard brakes on then 2 seconds off than you would from continuous dragging on brakes. You can also sit up and use wind to slow you down a bit. Most of all, don't ride like a prat.

Your bike appears to be a single-sided fork on a rigid MTB diamond frame, maybe with a small damper in the headset. I have no experience with single sided forks, but for the climb you'd want to lock out any suspension, and "lower" it if possible. For the road descent you may want to re-enable the suspension, I've got no experience, so no opinion either way on this.

Also, your single-sided fork.... Again I've never ridden a bike like this, it should be fine, but there are many increased forces at work. I suggest you do some more research on this.

My other suggestion is to not ride the MTB. See if you can hire or rent or borrow a suitable road bike and see how it compares. When I went from a 17KG rigid steel MTB to an 11KG aluminium road bike, my climb times dropped by 15-20%. They didn't feel any faster, so I have to rely on strava to show me my improvements.

Your other technique will be pacing - don't blast up the first climb and run out of herbs, learn your maximum sustainable pace, and methods for keeping to it.

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