Dunlop GT501s and now...chain information

[John S. (5594)]

Hi Folks,

Earlier this week - I spoke with Al Witt - a senior motorcycle tire specialist who is assigned to Dunlop's Consumer Affairs Department (Buffalo NY). A friendly and knowledgeable fellow - he provided the following tire inflation recommendations for their GT501 when mounted on the Honda CBX:

He suggested running a cold pressure of 34/38 PSI (front/rear) for this specific application. He also recommended against running pressures at the 42 PSI maximum rating (particularly in the front) and offered that handling, ride quality and tire wear would all suffer as a result.

When asked about Honda's original inflation specifications for the CBX - he commented (in general terms) that the OEM tires fitted back then had different construction - often a stiffer sidewall/carcass. This called for lower pressure settings than most modern tires.

The CBX Shop Manual recommends 28/40 PSI for the '79 Z Model (regardless of load). For the '80 A Model - Honda recommended 32/32 PSI for loads under 90 Kg and 32/40 for vehicle loads to up to vehicle capacity.

As mentioned - I have been running 34/40 PSI in the Dunlop 501 tires - and though I doubt it will make much of a difference - will now drop the rear a couple of pounds to Dunlop's recommendations. Certainly can't hurt :)

All the best,

John
San Jose, California

[sr71cbx]

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[EMS]

Almost as interesting and diverse as the oil issue I think we have finally come around to what was said on page 1 of this thread. :) Except Mark does not want to accept that the sidewall spec is a "maximum SAFE tire pressure when cold" for the TIRE as specified by the TIRE MANUFACTURER regardless of what bike it is put on. It has nothing to do with how well the rubber works when used on the CBX. Mark, you must have German ancestors, You know the saying: You can always tell a German, but you can't tell him very much.
Both Don and John refered to the manuals, so I checked mine also. I confirm the 79 and 80 data and for the 81 yet another pressure is given: 36f/36r when loaded up to 200lbs and 36f/41r when loaded 200 to max capacity.
Interesting that there was not only just a different rating between 79 and 80 although the bike did not change much, but also a different rating depending on load for the later models. Obviously a sign that changes in tires had something to do with it.

[sr71cbx]

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[Don]

Interesting that there was not only just a different rating between 79 and 80 although the bike did not change much, but also a different rating depending on load for the later models. Obviously a sign that changes in tires had something to do with it.

I think from '80 on up the got a different rear rim didn't they? Finally got rid of the ridiculous 2.15 inch rear rim which was all they offered in '79.

Possibly there are other types/series of tires which fit the wider rims that will not work on a '79, and possibly they call for different pressures???

Don

[John S. (5594)]

Hi Don,

Yep - the wheel widths crept up a bit over the years. Old news to the experts here - I'll still do a memory test for grins - my typing skills need honing too :)

The rear wheel on the '80 A Model got a bit wider - MT 2.50X18 vs. MT 2.15X18 for the '79 Z Model. The front rims are the same size for both the 79/80 models (MT 2.15X19).

From the tests I have read - the OEM tires fitted to the '79 were 3.50H19 4PR Dunlop F11 on the front and 4.25H18 4PR Dunlop K127 at the rear. The '80 went to V rated Dunlops of the same type and a wider 4.50V18 on the rear.

The '81 Comstar wheels went a bit further with a MT 2.50x19 front and an MT 2.75X18 rear. The front tires were the same 3.50V19 F11 Dunlops but the rear went to a 130/90V19 K127 Dunlop. For some reason I thought there was a further difference between the 81/82 wheels - but I don't have a manual at my fingertips.

I do know that the general philosophy regarding rear tires on the first "Superbikes" was changing quickly back then - the tire manufacturers were working hard to deal with all that new-found power (and were probably worried about safety/liability issues as well). I would venture that this is one reason why Honda initially recommended 40 PSI for the '79 rear (later dropped to 32 PSI for the slightly wider '80 rear at low load operation).

I suppose I have beaten this subject to death - sorry folks

John
San Jose

Just in case I haven't - a PS here: Though I am actually quite pleased with the Dunlop 501 tires on the '79 - I am going to fit Bridgestone dual compound BT45 tires on my alternate '82 rim set - have heard very positive things about them (Avons would be my next choice). Currently have Michelin Macadam MT50 tires on my '80 which seem to play quite well - but I do dislike the way they track the rain grooves on my favorite loop here - and then there is the "French" connection - oh well

[Don]

John,

If one was interested in putting a wider rim on a '79 (and still have it look "stock") which rim, off which model CBX, should I be looking for - Still needs to perfectly match the OEM '79 front wheel??

While I've got you on the "upgrade subject" should I be looking to change my '79 to a modern 530 chain and sprockets? I've read that there are smoothness and noise issues the lighter chain would "fix" - Any downsides to doing this?

Thanks,

Don

[John S. (5594)]

Hi Don,

Unfortunately - the wider Comstar wheels on the '80/'82 CBX's all have the stamped metal "spokes" reversed (and are painted black). If you want to match your existing silver '79 front wheel - it may be difficult. I definately would not even consider dissasembling any Comstar wheel.

The '79 project bike I am finishing-up came with an extra set of the black '82 Pro-Link wheels (along with dual piston calipers and slotted rotors). While I actually prefer the style of the silver '79 Comstars (especially with the Perseus Silver bodywork) - the wider late model wheels will get the nod on this Candy Glory Red "rider".

And I too am going to go with a 530 chain/sprocket conversion. I may also consider dropping the rear sprocket a couple of teeth - the stock gearing is too short for the open highway (nice for the hills though).

All the best,

John
San Jose, California

[EMS]

Don:

Look into the silver Comstar wheel Honda used on the Goldwing. The 1979 GL wheel looks exactly the same as the one for the Xes. It may not be an 18-incher, though. I don't know without looking it up

[sr71cbx]

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[EMS]

Pheew Guess that shows how much I know about Goldwings.
Well, if you can't install a drive shaft on a CBX, maybe you can modify the wheel hub and bolt a sprocket on it.

[Don]

I wouldn't have BOUGHT a CBX if it had a driveshaft! ;)

I'll look into the 530 chain - It's a shame there's not a matching rear rim about 2 1/2 or 3 inches wide somewhere

Don

[Don]

Don,the 530 chain conversion makes a world of difference.I had done it last year on my turbo '79 and also upped the gearing to 18/36 f & r to give it 2:1 final gearing and 4900 RPM @ 80 mph.

Can you buy an "endless chain" of the correct dimensions, or do you have to use one with a master link in it?

Don

[sr71cbx]

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[Jim-Jim]

Well, since we have left the tire subject and threaded our way over to chains , I'd like to ask a question about master links. What is the opinion about riveting -vs- clip master links. I was told by a 'Master' Mechanic awhile back that as long as the clip was pointing in the right direction (with the rotation) and firmly in the grooves, there was practically no outward force on it and the connecting plate took the pressure the same as a riveted link. He further commented that the clips got a bad 'rap' because some put them on backwards and, at high speed, they would come off. I would like to hear if any one has had practical experience with this (riveting is a chore). Jim-Jim