GTS musings - MP3 rim clearances, City Grips, wobble.
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Moderaptor
The Hornet (GT200, aka Love Bug) and 'Dimples' - a GTS 300
Joined: 26 Aug 2007
Posts: 38920
Location: Pleasant Hill, CA
Thu Sep 15, 2011 4:50 pm quote
GTS musings - MP3 rim clearance, City Grips, wobble.

Yesterday I started to ponder when reading of a fellow MVers who was having clearance problems with some MP3 rims fitted to their GTS. Some 4,000 miles ago I fitted Dimples with an MP3 (NOT the LT) rim as the shop didn't have any spare GTS ones to hand, complete with a rear Michelin City Grip tyre. The bike had a small discernible wobble beforehand (fitted with top-box, heavy bar-end weights) - which during our last long trip (2,900 miles, heavily laden) became a lot more noticeable. This was with a Pirelli GTS23 tyre up front, which was shagged out by the end of the journey. That was replaced with a new City Grip, and the wobble was no better, no worse.

I had already fitted the old GTS rim with a new rear MCG, so this morning I put it on - to help check clearances amongst other things. Wobble nearly completely gone - better than ever before!

The rear MCG on the MP3 rim, despite being good for another 4,000 miles in all probability, had some cupping and feathering which would just be one the edges of the straight-ahead contact patch. So I'm now thinking most of the wobble *I* have experienced has all been due to issues at the back-end, and nothing to do with the front. Next step is to get some stiffer buffers at the top of the rear shocks, to see if that has any effect.

Now to the MP3 rim part - yes, it has slightly different dimensions to the GTS rim - and although mine had a 0.5mm clearance to the exhaust support arm, I note some other folk have had no clearance at all - this could just be down to manufacturing tolerances or paint finishes. Suffice to say my MP3 rim has 5mm more 'meat' between the inside mounting flats and the outside of the central hole. This can cause binding if some bike's individual tolerances all conspire in the same 'wrong' direction. Pictures below:

2011-09-15-09-34-20-DSC01384.jpg
MP3 rim - 0.5mm clearance

2011-09-15-09-35-38-DSC01386.jpg
Cupping and feathering

2011-09-15-09-36-50-DSC01389.jpg
More MCG cupping etc (4,000 miles)

2011-09-15-09-39-50-DSC01390.jpg
Tyre outer to outer rim - GTS rim

2011-09-15-09-42-18-DSC01391.jpg
Tyre to inner flats - GTS rim

2011-09-15-10-28-54-DSC01392.jpg
GTS rim - 3mm clearance

2011-09-15-10-34-00-DSC01396.jpg
MP3 rim - tyre to outer rim

2011-09-15-10-34-42-DSC01397.jpg
MP3 rim - tyre to inner flats

Hooked
GTS 250ie "gone" & others vintage
Joined: 25 Jan 2011
Posts: 356
Location: Paris, France
Fri Feb 17, 2012 3:44 am quote
are mp3 rin safe on gts rear wheel?
The Beer Guy
2010 GTS 300 Super and 2015 Kawasaki Versys 650 LT
Joined: 30 Jun 2010
Posts: 4744
Location: Nelson County, VA
Fri Feb 17, 2012 4:31 am quote
Juju_paris wrote:
are mp3 rin safe on gts rear wheel?
If it fits it will work fine. I have a tire mounted on an MP3 wheel that I haven't put on the scooter yet. One thing I learned from jimc and my local dealer is that there are two different sizes: the LT and RL.

The LT is a bit wider, as Jim mentioned in his post above. According to my dealer, the LT version of the MP3 wheel *should* have only been available in Europe (good for me, maybe not so good for you). The part number for the RL wheel is 648625 and the LT version is 650692. I couldn't find a number on mine which leads me to believe that it's on the inside of the rim and I couldn't see it with the tire mounted.

But as to your question about the wheels being safe...other than the possible small difference in the width of the wheel, they function in every other respect the same as a GTS wheel. There are other users here with them on their scooters and all have said they work perfectly. I'll put mine on soon and will report back if I have any problems.
Moderaptor
The Hornet (GT200, aka Love Bug) and 'Dimples' - a GTS 300
Joined: 26 Aug 2007
Posts: 38920
Location: Pleasant Hill, CA
Fri Feb 17, 2012 4:33 am quote
Yes.
Ossessionato
X10 350
Joined: 12 Nov 2008
Posts: 2959
Location: London
Fri Feb 17, 2012 5:23 am quote
Sorry to be a idiot, but what do you mean by cupping and feathering, Jim, please?

(I've looked the pic's but am still no wiser )

Thanks.

(For the record, I'm on MCGs and find them to be fine. I'd always been on Michelin Gold Stds before, which I'd always been very happy with, and the MCGs seem no better/no worse when riding. I'm entirely happy with the MCGs, and they seem to be shaping for a long life, based on my amateur observations after a couple of '000 miles.)
Moderaptor
The Hornet (GT200, aka Love Bug) and 'Dimples' - a GTS 300
Joined: 26 Aug 2007
Posts: 38920
Location: Pleasant Hill, CA
Fri Feb 17, 2012 5:31 am quote
After prolonged stints at WOT or riding the twisties as hard as possible, the trailing edge as seen at the deep grooves will be seen to be worn away more than the leading edge. It's the depth of that 'feathered' trailing edge that determines if a tyre is worn out. 'Cupping' is the effect seen by virtue of that feathering, each segment of tyre looks rounded, as though there are a series of slightly raised 'cups' all around the tyre.

It can subtlely alter the ride characteristics - but there are no direct safety concerns.
Ossessionato
GTS 250 "Audrey"
Joined: 31 May 2008
Posts: 2117
Location: New Harbor, Maine
Fri Feb 17, 2012 6:02 am quote
Benelli Boy wrote:
Sorry to be a idiot, but what do you mean by cupping and feathering, Jim, please?
First, thanks for posting Jim!

[edit] Below are some links covering tire wear. The last I chose for the diagrams, simple and clear, but the explanations as to why are for a car. Which is good to know too.

[edit] While reading the following article, Motorcycle Tire Wear bear in mind JimC's comment: "Not too convinced by that m/c tyre article - firstly, left or right-side dominant wear on m/c tyre merely indicates which tyre of fast turn the rider prefers. Usually there's no difference, and whether you're in a lefty or righty environment makes no difference in the long run. Averaged over many rides you get the same amount of lean variation on each side regardless. A myth.

Later on he gets the 'leading' and 'trailing' edge nomenclature the wrong way round, and his reasoning rather falls apart because of that
. "

The photos are quite good.

[edit] The sketches below, though of a car tire, make a decent enough visual. I removed the car reference.
The following is from How to Read Tire Wear

Feathering

Feathering is a condition when the edge of each tread rib develops a slightly rounded edge on one side and a sharp edge on the other. By running your hand over the tire, you can usually feel the sharper edges before you'll be able to see them.

Cupping

Cups or scalloped dips appearing around the edge of the tread on one side or the other.
[edit]From Dunlop:You may not be able to entirely avoid cupping. Tire cupping or irregular wear is a somewhat common occurrence on all vehicles. On a four-wheel vehicle, you are advised to rotate your tires periodically to even out wear. Unfortunately, you do not have this luxury with a motorcycle because front and rear tires, unlike those on most four-wheel vehicles, are not interchangeable.
However, there are steps that can be taken to minimize cupping and uneven wear on a motorcycle: Maintain your motorcycle and particularly your front and suspension. Avoid hard braking whenever possible. Braking causes the tire to grab and wear in one direction. When braking is applied to the front tire, the load transfer over-flexes the tire and increases the tendency for cupping and uneven wear. Maintain your tire pressures. Under inflation and overloading of motorcycle tires are significant causes of cupping and uneven wear, particularly in association with hard braking and/or trailer use.
Once a tire begins to show signs of uneven wear, even following these steps may not improve the condition

Last edited by Paperino on Fri Feb 17, 2012 2:18 pm; edited 1 time in total
Ossessionato
X10 350
Joined: 12 Nov 2008
Posts: 2959
Location: London
Fri Feb 17, 2012 6:13 am quote
Thanks, Jim and Paperino. Much appreciated.

I now know what you mean. I'd noticed those effects on old tyres before (only to a small extent - but then again I wouldn't say I'm a sensitive soul), but not known that they had a name.

I'm learning all the time.......which can only be good, eh?
Moderaptor
The Hornet (GT200, aka Love Bug) and 'Dimples' - a GTS 300
Joined: 26 Aug 2007
Posts: 38920
Location: Pleasant Hill, CA
Fri Feb 17, 2012 6:34 am quote
Not too convinced by that m/c tyre article - firstly, left or right-side dominant wear on m/c tyre merely indicates which tyre of fast turn the rider prefers. Usually there's no difference, and whether you're in a lefty or righty environment makes no difference in the long run. Averaged over many rides you get the same amount of lean variation on each side regardless. A myth.

Later on he gets the 'leading' and 'trailing' edge nomenclature the wrong way round, and his reasoning rather falls apart because of that.

But the example pictures are fine.

The other article refers to car tyres, and is largely irrelevant to our PTW world.
Veni, Vidi, Posti
Neutrino MP3 492.7 AK, 2013 Moto Guzzi Norge
Joined: 29 Mar 2008
Posts: 21670
Location: Harriman, Tennessee, Tn
Fri Feb 17, 2012 6:36 am quote
Balance and tire pressure. when balancing be really picky on the weight placement and amount. After test weights are taped on the tire should be able to stop spin with the weights at 2,5,7,10 o'clock positions with out any roll. Do not place the weights on the outside spoke side. they should be on the inside of the rim. Clean really good with Alcohol before pressing down after final positioning of them. I use a piece of black duct/gaff tape over top just as an extra security measure to not throw a weight.
MV Santa
GTS250, 1960 VBA, 1975 VBC, 1980 P200E cutdown
Joined: 04 May 2010
Posts: 4377
Location: Sedgwick, Kansas
Fri Feb 17, 2012 7:51 am quote
As some may know I picked up a severe wobble when I switched from Savas ti MCGs. I reolaced the front MCG before it was half worn with a GTS23 and the wobble was substantially reduced but not eliminated. The MCG had no cupping and little feathering. The idea that the wobble could be coming from the back is counterintuitive but I will listen to any idea. I've heard of stiffer swing arm bushings and shock buffers. I know that the front has more than a little to do with it because a friend an I switched front wheels and my wobble was transfered to his bike with it. Waiting to see how jimc gets on with the shock buffers. Some pepole have had good results with a new adjustable front shock. Spendy, but I would do it if I was sure it would cure it.
Petty Tyrant
GTS250 GTS300 MP3 500
Joined: 11 Oct 2005
Posts: 29654
Location: Bay Area, California
Fri Feb 17, 2012 8:01 am quote
vintage red matthew wrote:
As some may know I picked up a severe wobble when I switched from Savas ti MCGs.
Savas are very well known for two things:

1) Masking the front wobble
2) Being shitty tires

Ossessionato
07 GTS250(RIP), 13 GTS300, Several Lambrettas
Joined: 25 Apr 2007
Posts: 2695
Location: Raleigh, NC
Fri Feb 17, 2012 8:03 am quote
Re: GTS musings - MP3 rim clearances, City Grips, wobble.
I came to that conclusion several years ago:

Rear Tire Pressure is Key to GTS Headset Wobble
jimc wrote:
....So I'm now thinking most of the wobble *I* have experienced has all been due to issues at the back-end, and nothing to do with the front. ...
Lurker
GTs 300 Super
Joined: 31 Mar 2013
Posts: 2
Location: Beerse Belgium
Wed Apr 03, 2013 3:07 am quote
Had the same problem with my MP3 rims
The " offset " from the MP3 wheels & the GTS wheels is NOT the same
There is a 5 mm difference
Because of that the MP3 wheels are NOT in the middle under the scoot !!!
You can see that and measure that
So i took my rims to a machine repear shop , and they took 5 mm
alu meat " OFF " the inside mounting flats ( inner flats )
Now my both wheels are in the middle under the scoot
And the " clearance " problem of the rear wheel is solved
Dont forget to shorten your wheelbolts by 5 mm
And you have to take of some ( 1 & 2 mm ) material from your
rear brake calliper for clearance

nothing to it

Grtz Ertje Belgium
Enthusiast
Joined: 19 Mar 2012
Posts: 80
Location: uk
Wed Apr 03, 2013 10:10 am quote
mp3 rims
when you say 1 to 2mm on the caliper what do you mean
Lurker
GTs 300 Super
Joined: 31 Mar 2013
Posts: 2
Location: Beerse Belgium
Wed Apr 03, 2013 2:47 pm quote
I mean the brake clamp
its made of alu. There is material enough so dont worry

Grtz

Erny

Belgium

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Lurker
2015 - VESPA GTS300ie | 71' Lambretta GL125 | 82' P200E |
Joined: 12 Jan 2020
Posts: 4
Location: Houston, TX
Mon Jan 13, 2020 9:02 pm quote
Anyone done this with a 2015 or newer???
I am having clearance issues with the ABS Tone Ring... Is there any tricks or tips for proper spacing and use of MP3 Wheels?
Ossessionato
2015 GTS 300 Super (Melody)
Joined: 22 Apr 2015
Posts: 2612
Location: Asbury Park, NJ
Mon Jan 13, 2020 10:16 pm quote
This has to set something of a record for call-and-response times on an MV thread!
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