Metzler Roadtec

[Roy gardner]

Has anyone had any experience of Metzler Roadtec tyres on short Tonti (pre-LM III) models? I just fitted a pair to my Lemonvert, 76 Convert with Mk IV motor, Convert trans.
I was told by the salesman that they would tip into corners easier than the old Lazertec, and they do, and the bike remains well balanced in the corner, doesn't drop in & need to be held up as I expected, really nice.

But, here's the BUT, under hard braking in a straight line, from 70-80MPH, it weaves violently! Not lock to lock, but bad enough to be scary and getting worse as it slows, to the point where I get off the brakes really quick at about 50 in the interest of self preservation!

I suspected I had a bad damper, so I fitted a new pair & tried again, still does it. I swear it never did that with the old Lazertecs which I have used for years on most of my Guzzi, V7 Sport, 850T, as well as the Convert for 7 or 8 years.

I run standard integrated brakes but with an 09 caliper under the front lever, nice feel. Recent braided lines, new pads, overhauled calipers & master cylinders all about a 18 months ago and no sign of weaving until now.

Any ideas out there?

.

[Tony F]

What pressure are you running?

[Roy gardner]

Yea, forgot to mention that. 32 front, 34 rear, per the book.
I have run 36 rear with Kendas as the book recommends for loaded, but was convinced that some of the wear was over inflation. 

[Tony F]

I would try more air pressure, the 36 you were running with the Kendas sounds more like it for the front and 39 for the rear. It may even like a bit higher than that. The old Guzzi factory pressure recommendations come from a time of much heavier and stiffer tyre construction.

Do you know the pressure gauge you are using is accurate? A 10% variance is 3 lbs which could be significant.

Is the weave triggered when using just the front brake or when both brakes are used together?

I suppose you checked the steering head bearings when you overhauled the forks? Is the alignment of the forks in the yokes correct? Do you have a fork brace?

What wear were you seeing on the Kendas that leads you to think they were over inflated?

Tony

[Roy gardner]

OK, increased pressure is worth a shot.
Same gauge I've used for years, so same pressures as previous tyres & it's generally matched gas station inflators. Not to say it isnt out though.

Was using both brakes together, so there will never be equal bite on both discs with integral brakes of course. Didnt try with one only.

Yea, bearings are good, lubed while forks were off. Rolled the stanchions on vee blocks under a DTI when I put it all together the first time, less than .005" TIR and no wear on the chrome. Eyeball through the legs indicates parallel and the axle slides in & out with only finger pressure. I am a bit fussy about fork alignment, I spend a bit of time when assembling forks to ensure that the axle is an easy fit. That usually entails "manipulating" the mudguard stay tubes on a steel guard model during first assembly.
Assembled with two piece Spada springs & standard Guzzi dampers last major rebuild. Rides nice, supple with no wallow. Receives compliments from other Round Barrel owners who ride it. No fork brace, relies on the stiffness of the old mudguard stay tubes fitted to the steel mudguard models. Superior to the plastic guard types. 
The centres wear out of the Kendas on the rear, like they all do. It was a throwaway comment from another longtime Guzzi rider from Canterbury that made me review the rear pressure. I get my money's worth with pretty even wear across the Lazertecs on the front, even riding around here in Marlborough, there are enough corners over the Weld Pass & Whangamoas to scrub a bit off the sides.

The big issue here, as I see it, is that the Lazertecs never behaved like this, It has happened with the change of tyre, I am sure of that.

I have ordered a new Lazertec & will fit it to prove the point. The shop has suggested sending the Roadtec back to Metzler for checking which is fine but I dont believe they will come up with any answers unless they fit it to another Tonti Guzzi, hence the question here. I'm OK to fit it to my Egli Vincent, that is 100Lb lighter, has 38mm Marzocchis off a 650 Benelli & a Grimeca 4LS brake, but it will be another year or 2 before it's ready for a front tyre, it looks like tyre wear rate is half that of the Lemonvert!

What do you ride?

[Bulldog9]

During my trip to Nova Scotia last summer I was forced into buying a new set of tires due to encountering road debris which produced two flats. I was blessed to find a local dealer a Harley shop of all things with a set of metzeler roadtec m3s. I was able to be back on the road and heading north within 2 hours.

I put them on a Norge, found the same, the roadtechs stick well, are great in the twisties but hard braking produces some instability from the front with slight weaving. It only happens in very hard braking, and only noticeable because of the immediate change from the last set of tires. I actually forgot about it until I saw this post. I attributed it to the fact that the m3's are probably made for a lighter sport bike not a fully loaded sport touring rig.

They've held up better than I thought, have 4,000 miles on the set right now, and probably have another two left..

[Roy gardner]

Thanks Bulldog. I suspect that your Roadtec M3s are radials? Nonetheless, it is interesting to hear that type exhibits similar characteristics. They all have similar tread patterns.

So I took Tony F's suggestion & added pressure to 38 and tried again with various braking combinations, just front, just rear and both with feathering front. 
Same result, still a weave, increasing as the bike slowed.

The only time there was a reduction in weave was using the rear pedal only, although the front disc is working, it does not create enough braking force to generate the weave. 
 
The new Lazertec has arrived in the shop, I will look at changing it Monday.   

[Tony F]

Hi

Did increasing the pressure to 38 make any difference at all? It seems that the braking loads are overwhelming the tyre! What is the maximum pressure marked on the tyre wall?

I was intrigued by this issue so went looking through a few roadtec reviews on the net for any reference to the problem.

In the comments following one review of the tyre there was mention of an HWM (heavy weight motorcycle) version of the tyre from a BMW R1200GS rider who was adamant about the need to use it on heavier bikes:

http://www.tyrereviews.co.uk/Tyre/Metzeler/ROADTEC-01_2.htm

"Given 100% while driving a BMW R1200GS (180/55 R17 W) on a combination of roads for 5,000 spirited miles
Best tyre ever. In my 27 years I tried everything. Last I used were bridgeStone Battlax30, Metzeler roadtec Z8, Dunlop Sportmaxx III and Michelin PR4. Dunlops are sporty, Michelins are great in cold, but Roadtec 01 outperform both. Tyre wear is also good, have to use HWM model on heavy bikes, so don't wine, if U use wrong tyre on your bike and get bad results. Great handling, great wet grip, great feedback as it could be on RT with ESA, great comfort, great handling. I will buy and buy them again :)
 6 - tyre reviewed on April 17, 2018"

There is further mention in this article about the HWM version and the heavier construction:

https://www.rideapart.com/articles/247377/metzeler-roadtec-01-tire-review-dr-moto-review/

The HWM rear tyres have an additional belt and the fronts have stronger side wall construction.

Which version are you using?

Tony

[Roy gardner]

Thanks Tony. No, as above, 38PSI made no difference at all.
Interesting about the HWM series, I suspect that the sizes quoted would be radials as I suspect Bulldog's Norge would be. I will ask my dealer about the HWM series availability in 100/90 bias ply.

Tonight I picked up the wheel with the new Lazertec fitted by the shop. For a "tyre expert" outfit I was pretty disappointed, they hadnt put the red dot balance mark at the valve, when I quizzed him about he shrugged & said 'they dont make any difference" then said "we put thirty grams of balance weights on"
Guess where they were, at the red dot, opposite the valve!

That's why I work up a sweat fitting my own with a rubber hammer, I know I have them right. Then I balance them by letting them hang on the axle with no calipers fitted.
Interestingly, the new Roadtec, when I fitted it, needed no balance weights. I watched the shop guy put it on his balancer which said it needed 5 grams but couldnt work out where, & I could see the spindle running out of true. I told him I didnt rate his balancer right there!

So the result of fitting the new Lazertec; much better braking stability than the Roadtec.
I could still induce some weave under hard braking from 70 MPH but it was not as violent as the Roadtec and felt controllable.

Why? I have had time to give that some thought, I reckon its the 09 caliper under the hand brake, it creates so much bite that it's twisting one fork leg more than the other. If I dont squeeze it so hard, the weave is noticeably less.
Thats the down side of Integral Brakes Vs 2 front discs working together.

Would I fit another Roadtec? No, not on the front of a Guzzi. I dont expect they will take back my tyre with 100 miles on it. I will fit it to my Egli Vincent.

I will keep the Roadtec on the rear & see how it wears, all reports I see indicate 10% better life.