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Old 06-08-2012, 12:16 AM   #16
boxerboy81
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On my R100RS I test for headshake regularly. I have a couple of nicely sloping hills close to home where I do this. This is an easy test to do but less valid on old tyres I guess.

Doing 45-60 kph down a slight hill, I loosen my grip on the bars. If it starts to headshake, the next thing (other than tighten the grip) I do is check the tyre pressure. I run 36/38 one up, 36/40 loaded.

If that doesn't help (or if the tyre pressure was ok) I then tweak the head stem bearings a tad tighter. It might only be a couple of mms. Mark the adjuster with an adjacent reference so you can see how far it's moved after you've tightened the large centre nut.

On a flat road, when riding at slow speed eg 45kph, if the bike feels like it wants to wander mildly left to right to left to right....has a slow weave, then the bearings are a tad tight. Loosen 2mm.
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Old 06-08-2012, 07:44 AM   #17
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Back in the days when some folks used their bikes as their only transport all year round it was not uncommon to fit a sidecar to get you through the worst of the winter.

With the chair the tires wore flat , and lost their rounded profile. Come spring if you removed the chair but didn't change the tires you soon had a reminder in the form of a full blown tankslapper.

You didnt ever forget that lesson.

Now these old tires started off much flatter than tires are today, so the problem is never going to be as bad these days, but I still change my tires when they are 70% worn, or earlier if they have flat spotted.

The only two dual purpose front tires that haven't scalloped on my G/S are Avon Distanzas, and Pirelli Scorpion A/T s.

The A/T is lasting well too, it looks like it will last as long as two rears, might get about 6000 km out of it.
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Old 06-08-2012, 09:04 AM   #18
supershaft
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Quote:
Originally Posted by boxerboy81 View Post
On my R100RS I test for headshake regularly. I have a couple of nicely sloping hills close to home where I do this. This is an easy test to do but less valid on old tyres I guess.

Doing 45-60 kph down a slight hill, I loosen my grip on the bars. If it starts to headshake, the next thing (other than tighten the grip) I do is check the tyre pressure. I run 36/38 one up, 36/40 loaded.

If that doesn't help (or if the tyre pressure was ok) I then tweak the head stem bearings a tad tighter. It might only be a couple of mms. Mark the adjuster with an adjacent reference so you can see how far it's moved after you've tightened the large centre nut.

On a flat road, when riding at slow speed eg 45kph, if the bike feels like it wants to wander mildly left to right to left to right....has a slow weave, then the bearings are a tad tight. Loosen 2mm.
That's a good way to put it bb. When you are in the neighborhood, there isn't much turning between right and wrong. In other words, perfect is a damn touchy spot.
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Old 06-08-2012, 04:56 PM   #19
patanga OP
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Interesting background

Quote:
Originally Posted by Beemerboff View Post
Back in the days when some folks used their bikes as their only transport all year round it was not uncommon to fit a sidecar to get you through the worst of the winter.

With the chair the tires wore flat , and lost their rounded profile. Come spring if you removed the chair but didn't change the tires you soon had a reminder in the form of a full blown tankslapper.

You didnt ever forget that lesson.

Now these old tires started off much flatter than tires are today, so the problem is never going to be as bad these days, but I still change my tires when they are 70% worn, or earlier if they have flat spotted.

The only two dual purpose front tires that haven't scalloped on my G/S are Avon Distanzas, and Pirelli Scorpion A/T s.

The A/T is lasting well too, it looks like it will last as long as two rears, might get about 6000 km out of it.
Thanks BB. Makes sense regards the chair experience. What do you mean when you say that you "might get about 6000km out of it"?.. That sounds very light on k's & around half life from what I would typically expect. Mind you I run them longer than 70%. Maybe I've been expecting too much from the BT45's re tread wear cupping & the wobbles?

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patanga screwed with this post 06-15-2012 at 07:57 PM
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Old 06-09-2012, 11:05 AM   #20
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Thanks BB. Makes sense regards the chair experience. What do you mean when you say that you "might get about 6000km out of it"?.. That sounds very light on k's & around half life from what I would typically expect. Mind you I run them longer than 70%. Maybe I've been expecting too much from the BT45's re tread wear cupping & the wobbles?
Except for Marathons and the like, I am lucky to get 3000 miles out of any back tire I have ever run and I am lucky to get two back tires out of a front tire. I hear the same story from others wondering how some people get all the miles out of their tires. I am lucky to get 1500 miles out of certain Metzelers and other tires. I can get more miles out of a Avon race tire that has at least twice the grip!

I run my rear tires down to the wear bars all the time. Front tires? I change them way earlier than that. Front tires are a completely different animal. I remember telling a customer that his front tire was down to the wear bars and he asked what about all this thread I see? I said come over here to the left side and look at your tread. See? It's down to the wear bars right along here and that is very obviously where you need the tire the most and right there it is gone! That screws with the profile big time and front tires are mostly about the profile. At least we are not running dual sport tires. Most of those front tires need to be changed WAY before 70% for horrible cupping and a profile that really isn't a profile anymore.
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Old 06-09-2012, 11:10 AM   #21
MightyManfred
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I've run Avon RoadRiders and Bridgestone Spitfires on my '87 R80RT and get over 7,000 miles on them. Between 12 and 14 k miles on the front.
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Old 06-10-2012, 05:10 AM   #22
Beemerboff
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Patanga - riding in Oz is not conductive to long tire life, especially in the drier and hotter states.

Although I drag a bike out most days regardless of the weather I don't ride on wet roads much, and almost never on frost /black ice.And 3 months of the year it might be over 100f.

Speed restriction enforcement means that most of my riding on sealed roads is on twisting back roads, on bumpy, slippery, spray seal, which of course is hard on tires.

Our unsealed roads and tracks are crap too - most of them have a loose layer of gravel on the surface, so both wheels are permanently moving around , and spinning under acceleration.

And its probably about time I had the rear shocks on the G/S and the /7 rebuilt too - both are well overdue, and that cant be helping things much.

But riding style must come in to it too.

I keep the wick up on the Beamers - I don't ride in groups so I can push on as I please, and I rarely get passed by anything.
I ride real loose too , I usually ride on roads I know well , and I run hard up to my usually very late turn in point then chuck the bike over and into the corner and scrub my way through. I keep the bike moving around the road most of the time too.

I inherited a set of Deathwings on my XT600, and I ride that completely different. The first time I chucked it into a corner the front 'wing stepped out a foot, so it gets ridden like it was on black ice - as near to upright as possible most of the time , and as much of the cornering done by weighting the footrests as by handlebar input. And I feed what feels like the 30 HP in real carefully too. Looks like I will be able to add another 5000 km to the 1500 km the PO put on them.

I dont know how anyone can get 10,000 miles/16,000 km out of a tire. I try to imagine it, but all I get is a picture of a guide dog and a white stick----.
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Old 06-11-2012, 05:40 AM   #23
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Quote:
Originally Posted by Beemerboff View Post
Patanga - riding in Oz is not conductive to long tire life, especially in the drier and hotter states.

I don't know how anyone can get 10,000 miles/16,000 km out of a tire. I try to imagine it, but all I get is a picture of a guide dog and a white stick----.
Hi BB & thanks for your feedback. Most of my riding tends to be day to day suburbs and city stuff, so not a lot of excitement there. I do go on week end rides at times and chuck the bike around a little, but not to the extent that I'm ever fully committed. Brisk riding yes, but I don't trust the public roads and traffic enough to step out in faith. There are too many roadside reminders for my liking. I run the pressures up at the higher end (40psi) and it's rare that I would get less than 10 - 12,000k's out of a set of tyres. I'm obviously not punting hard enough:)

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Old 06-11-2012, 10:55 AM   #24
supershaft
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Funny. Riding around suburbs wears my tires out faster than anything. At least the back tire. For how I ride, 40psi won't work. But lower pressures don't cost me any tire wear IMO. I think higher pressures wears the center of my back tires even faster but then again I don't ride to conserve tires although I do wish they would last longer!

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Old 06-11-2012, 11:04 AM   #25
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You haven't run into that phenomenon? Your lucky if you haven't. Bikes tend to go into tank slappers under those conditions. Why? From what I have read physics. I can't explain it. I have read about it. It's a bit more complicated than figuring out your tranny shimming, for instance.

It was not a contentious query at all; quite the contrary.
My RS is only unstable at that exact speed range and after adjusting,readjusting sag,tire,tire pressure,blah,blah,blah I wonder why and, moreover, if it actually can be eliminated?
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Old 06-11-2012, 11:19 AM   #26
supershaft
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It was not a contentious query at all; quite the contrary.
My RS is only unstable at that exact speed range and after adjusting,readjusting sag,tire,tire pressure,blah,blah,blah I wonder why and, moreover, if it actually can be eliminated?
And that wasn't a contentious reply! They all are! Some "gurus" claim that they can make airheads wobble free. 100% BS!
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Old 06-11-2012, 11:52 AM   #27
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But what is it about that 50-30,literally, since it does not seem to occur 30-50?
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Old 06-11-2012, 12:00 PM   #28
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It's complicated physics if I remember right. The size and weight of most wheels and the rake and trail of most setups. Throw in the absolute weirdness of what our tires do. The tiniest bump and fork flex. Rider weight and so on.

The slowing down part has to do with effective rake and trail, weight bias and engine gyroscopics. Something like that?

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Old 06-11-2012, 03:08 PM   #29
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Quote:
The slowing down part has to do with effective rake and trail, weight bias and engine gyroscopics. Something like that?

I don't know for certain, but that sound reasonable...
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Old 06-11-2012, 04:49 PM   #30
supershaft
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Somethings I just accept for what it is. We all have bikes with that danger zone. It's easy to fall into coming into a stop sign or whatever and taking your hands off the bars to fool with your tank bag or what have you. BTDT!
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