Moulton TSR rear tyre wear.

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Mick F
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Moulton TSR rear tyre wear.

Postby Mick F » 11 Oct 2018, 11:22am

I've noticed how quickly the rear tyres wear on my Moulton.
1,500miles is about it.

Schwalbe Durano
Conti Sports Contact
Conti GP

The front ones OTOH seem to last and last and last.
The bike came with Schwalbe Durano tyres which were horrible, so I splashed out on a pair of Conti GP. The rear one lasted 1,500, the front one is still on and absolutely fine 5,200miles later.
I fitted a Conti SC onto the rear. That lasted 2,900miles. Much better!

I fitted one of the original Duranos to the rear after the Conti SC wore out, and after 1,100miles I've suffered two punctures within 26miles of each other as the tyre is wearing thin. Just fitted a brand new Conti SC on the rear ................... and the Conti GP on the front is still perfectly fine at 5,200miles.

I can only think that a TSR is very heavy at the rear end and lightly loaded at the front. I must try and work out where the centre of gravity lies when I'm on it.
Mick F. Cornwall

Brucey
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Re: Moulton TSR rear tyre wear.

Postby Brucey » 11 Oct 2018, 11:37am

tyres wear faster on small wheelers anyway but IMHO it is the climbing that does it in your case. Pretty much all your weight will be over the rear wheel when climbing a steep hill and there is a large driving force too.

Note also that with small wheels (at any given tyre width/pressure) the contact patch is shorter and wider than with bigger wheels. This may -under certain conditions- mean an increased chance of slippage under load.

The other thing that may be wearing the tyre faster than normal is braking using the rear brake. Before the tyre skids wholesale, it will hop and skip a little (aided and abetted by the suspension, which is stiffer than it needs to be once the weight is transferred forwards) over bumps and this hopping and skipping may cause greatly accelerated tyre wear.

One way of maybe telling if there is substantial slippage or skipping is to use a cycle computer on both wheels and see that they always read the same speed or not.

IME in less hilly terrain it is normal for the rear tyre on a moulton to wear two or three times faster than the front, not five or ten times faster. Note that once a tyre is a year or two old, it will usually be a lot harder than a new one of the same type, so its wear rate will be even lower (and so will the grip....).

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Mick F
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Re: Moulton TSR rear tyre wear.

Postby Mick F » 11 Oct 2018, 1:49pm

Sort of makes sense, Brucey.
It's the up-hills.
The bike has done a total of 5,725miles as of now and chewed its way through three rear tyres.
Looking at my records, just this year it had done 1,260miles with 126,250ft of ascent.

Spending a few minutes researching, in the 5725miles, it has climbed a grand total of 597,405ft of ascent.
That's just a bit over 104ft per mile. :shock:
Mick F. Cornwall

Samuel D
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Re: Moulton TSR rear tyre wear.

Postby Samuel D » 11 Oct 2018, 2:36pm

Yeah, it’s the climbing that does it rather than the weight per se. The rear part of the contact patch is loaded in shear and slips under drive torque, scuffing the road surface every revolution. And since the wheel is small, that revolution comes around often.

Additionally, since you’re no lightweight, all of this happens at a contact pressure at the upper end of what the tread rubber was designed for.

In such a case I would put the new tyre on the front each time and swap the slightly used front to the rear. That would make sure both tyres are relatively young at all times. But I’m sure you have your reasons not to do that.

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Mick F
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Re: Moulton TSR rear tyre wear.

Postby Mick F » 11 Oct 2018, 2:56pm

Yeah .........
Just looking at 2015 - the year before I bought Moulton, and that year only on Mercian, I'd climbed 109ft per mile, but historically, Mercian hasn't worn out rear tyres very much at all. Yes, more than front ones, but I swap them over regularly and eventually fit a complete new pair. Six or seven thousand miles or thereabouts.

Not done that with Moulton because it happens so quickly. I wasn't ready for it originally, so the pair of Conti GPs I put on there 300miles after buying the bike, the rear one wore out so fast, it wasn't any use for the front. It was down to the canvass in a couple of places and on one of the sides too. The front one, I took off, and fitted a pair of Conti SCs keeping the front GP as a spare.

The rear one wore out before I checked, and that was knackered, so I put the front onto the rear and put the original front GP back on the front.
The rear SC wore out, so I fitted one of the original Duranos. That has not actually worn out, but two punctures within 26miles tells me something.

In the meantime of all this, I bought a pair of Conti SCs on offer and they've been waiting in the wings. Just fitted one to the rear and left the GP on the front. I expect the SC on the rear to wear out before the front GP even though it's long in the tooth now. Due to having small wheels and having mudguards, you can't see the rear tyre tread unless you turn the bike over.

The moral to all this, is keep an eye on the rear tyre wear FAR more than you think necessary on a normal bike even if you have to go to a bit of trouble to look.
Mick F. Cornwall

igauk
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Re: Moulton TSR rear tyre wear.

Postby igauk » 12 Oct 2018, 1:41am

Interesting discussion. I've got Panaracer Minits Light PT on my TSR, but they've only done about 600 miles. I'll update as and when they wear.
Aravis Audax, Moulton TSR

rogerzilla
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Re: Moulton TSR rear tyre wear.

Postby rogerzilla » 12 Oct 2018, 10:27pm

Rear tyre wear is mostly through scrub on the road, especially when honking out of the saddle. Fixies with no rear brake get through rear tyres just as quickly, unless you're an inveterate skid merchant on a normal bike - unlikely if you're over 14 and have to pay for your own stuff.

Any sideways flex or play will make scrub worse, since the tyre is then pointing in a different direction to the direction of travel.

Incidentally, you shouldn't rotate tyres from rear to front. Rear tyres take on a flattened profile and you don't want a worn tyre on the front anyway, since the consequences of failure are greater. When the rear tyre wears thin, put the old front one on the rear and buy a new front one. It all costs the same in the end.

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Re: Moulton TSR rear tyre wear.

Postby Brucey » 12 Oct 2018, 11:37pm

I'm still suspicious of the rear wheel hopping and skipping on the brakes; Mick lives in a hilly part of the world and uses the rear brake more than some folk do. Once the weight has transferred to the front wheel (braking on a downslope) it won't take much to kick the rear suspension so the rear wheel is unloaded a little and that can make the rear tyre do a micro-skid as it regains traction. If it happens that will wear the rear tyre PDQ.

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gazza_d
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Re: Moulton TSR rear tyre wear.

Postby gazza_d » 13 Oct 2018, 6:34am

I've tried both Durano and Kojak on my APB and TSR and found that they both wore down within about 2000 miles or so on the back.
In contrast Marathon and Marathon Plus easily last 4000-5000 miles easy.
Presumably this is down to the smaller lighter tyres just having less rubber, and possibly being a "stickier" compound so scrubs off earlier.
I'm not a hugely fast rider, so didn't find huge performance gains from the lighter tyres and am not on 20 x 1.35" M+ on both as a decent trade between performance, lightness, reliability and wear for me personally

The Moultons are generally well designed with a balanced CoG, but both of mine have hub gears which I'm sure shifts that slightly.
I also ride with saddle forward on rails as much as possible. I read once that improved the performance of the Moulton, and I seem to find it so (although it could be just my confirmation bias). In contrast my conventional bikes have always had the saddle further back

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Re: Moulton TSR rear tyre wear.

Postby gazza_d » 13 Oct 2018, 6:36am

And just to add that my TSR came wit the Conti Sport contact II which punctured is I even dared to ride past a bush with thorns.
They rode well but I got punctures practically every time I rode so they ended up in the bin as they were terrible

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Mick F
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Re: Moulton TSR rear tyre wear.

Postby Mick F » 13 Oct 2018, 9:39am

gazza_d wrote:The Moultons are generally well designed with a balanced CoG, but both of mine have hub gears which I'm sure shifts that slightly.
I've yet to measure where the COG lies. Need to do it with me on board of course sitting normally. I can see the weight on the bathroom scales front vs rear using blocks to level up the bike. May get to this shortly, but I will do it.

Just a quick measurement, the rear edge of the saddle is only 3" forward of the rear axle, which is the same as Mercian which has short chainstays and close clearances.

I would suggest that the GOG isn't well balanced, but we'll see.
Mick F. Cornwall

Brucey
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Re: Moulton TSR rear tyre wear.

Postby Brucey » 13 Oct 2018, 9:53am

It is often assumed that front:rear loading is about 45:55 but IME it is usually a lot more rear biased than that. To a good approximation the CoG of the rider on a bike is usually very close to the rider's navel. This normally ensures a strong rearwards weight bias. The bike is only about 10-15% of the entire weight but that is also rear-biased unless a front load of some kind is carried.

You can get some idea of the weight distribution expected on a moulton (which isn't wildly different from a lot of bikes BTW; the wheelbase is about the same as a lot of bikes) by looking at the spring rates of the suspension. Placing most of your bodyweight over the front of a moulton uses up most of the available suspension travel immediately (the spring rate is very soft) but at the rear it moves a lot less.

Image
check out the wheelbase vs riding position in the top right corner. Spaceframe moultons are like this too

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Mick F
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Re: Moulton TSR rear tyre wear.

Postby Mick F » 13 Oct 2018, 9:57am

Done it. :D

Moulton TSR without me on it.
Front 5.9Kg
Rear 7.6Kg
This seems fine to me.

Moulton plus me.
I was sitting normally with hands on the tops, and leaning gently against the wall.
Front 34.8Kg
Rear 58.5Kg
This means that when I'm on it, there's 24Kg more on the rear wheel than on the front. No wonder the rear tyres wear quickly!
Mick F. Cornwall

Brucey
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Re: Moulton TSR rear tyre wear.

Postby Brucey » 13 Oct 2018, 10:28am

another way of putting it is that the weight distribution is about 63:37, on the flat. Because the CoG is so high up, there is a lot of weight transfer even on a gradient, leave alone when the brakes are used.

Thus the weight distribution could easily go to 80:20 when climbing a steep hill , or 20:80 (or worse) when the brakes are used on a descent.

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Mick F
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Re: Moulton TSR rear tyre wear.

Postby Mick F » 13 Oct 2018, 10:50am

That sounds right.
Mind you, on a descent the weight doesn't shift forward as per the rider being in the same position as on the flat.
I tend to move my weight to the rear when descending and braking, so that would skew the figures a bit towards the rear in that scenario.

It's obvious that the rear tyres wears much faster due to the extra weight. I wonder how Moulton weight distribution compares to Mercian statically, but I would imagine it's similar. The difference is the suspension when riding of course.

As a matter of interest, Mercian has a wheelbase of 102cm and Moulton 107cm. (just measured them)
Mick F. Cornwall