TYRES, TIRES and RUBBER - FITTED to EARLY CB750's

[Steve Swan]

so then there is this thread, it seems we established the Brighton bike, 2110, had Superspeeds on it....  http://cb750sandcastonly.com/smf_forum/index.php?topic=281.15

[Sgt.Pinback]

In the August 1969 issue of "DAS MOTORRAD" (A German Bike magazin) a sandcast had been tested.

Text says that tyres are in Japan produced (lizence) Dunlop "nylon cord".

I have no idea what those are.

[markb]

Wow, a lot of good info on that thread. I had forgotten some of the posts I made. 

[Steve Swan]

it could make sense the p-p bikes had Superspeeds and the production bikes did not.  only 4 bikes vs. thousands of bikes, contract agreements, who knows what else personalities, politics and ego's may have been in play at the time.  what 'evidence' we have points at Dunlops being on early prod.vins and while i could tend to believe Bridgestone tires were not on early sandcasts and may not have been on any sandcasts, i suggest the necessity of staying on the look out tire types on any new sandcast acquisitions anyone might have.  

My now owning a 1967 Bridgestone 350 GTR, having read a bit of information about Bridgestone, the story of Honda threatening to quit buying tires from Bridgestone, from what i have read may be true and happened during the time Honda was working on the CB750.  Bridgestone quit production 1971.

[Steve Swan]

a bit of Bridgestone history:

While production at the Bridgestone site was busy the motorcycle production side was more of a side line to the tyre manufacturing and profits earned didn't stay within the motorcycle division but were absorbed by the tyre division. Unconfirmed rumours spread that other Japanese motorcycle manufacturers made it clear to Bridgestone that if they pursued their competitive attitude in motorcycles on and off the track they would find themselves with no home market for their tyres, the big four had the view they were putting money into a competitor by buying their tyres. A perhaps more plausible reason was the company’s decision to focus on its tire business rather than invest in the technology needed to meet new clean-air and noise standards. The dealer and sales network in the U.K. had already gone by then, and the demise of the network in other countries swiftly followed.  Both tyre and motorcycle production took place in adjoining sections of the same crowded factory and expansion of one would be at the expense of the other, the alternative was heavy investment in a new factory, also the increasing value of the yen against the dollar was cutting into profits and didn't bode well for the future either.It soon became apparent that corporate interest in continued motorcycle development was slowing with late sixties "new" models that were merely painted over variations of earlier ones or given high pipes, chunky tyres and called scramblers i.e. the 350 GTO. Dealerships began bailing out and then there was the environmentalist pressure against two-stroke engines in the U.S.Following the 1971 model run Bridgestone closed the motorcycle division at Ageo with most of their tooling sold off to a Taiwanese firm named BS Tailung.  

[markb]

As sometimes happens (seems more and more ) my memory was incorrect about the size of the Dunlop K87. Here’s a pic of a new Dunlop K87 on the left and a used Bridgestone Superspeed on the right. They are amazingly close in dimension (width and diameter) and tread pattern. 

[Steve Swan]

one major problem with the new Dunlops, they are good for less than 2,200 miles max of normal riding; i.e., no smokies, no burn outs, no stop light to stop light drag racing, no sustained high speed; just rpm's occasionally up to 6,500 - 7,000, mostly under 6,000.

[vnz00]

My pre-2000 bike was purchased with what I believe were original fitment Dunlop Gold Seals, F3 front and K87 rear.  I think the F6’s came in as a later replacement for the F3’s early to mid 70’s. These tyres are the ones mentioned on the later K0 rear guard decals as well.  My bike had 8000 miles on it so if they weren’t original, they were likely replaced same for same.  I’ll post pics shortly of the tread patterns.  

Here’s a pic in the meantime of a Tyre decal from a spare K0 Guard I have.  This shows both Dunlop’s and bridgestone mentioned too.

[Steve Swan]

Steven, that "tire decal" on a pre2xxx bike is, at least to me, an interesting detail.  clearly appears faded brown and original to bike.  i was always under the impression those "tire decals" appeared post-7414...

[vnz00]

Indeed the decal is from a K0 guard Steve, not from my sandcast.  Sorry if it wasn’t clear.  I’ve amended my post.  I included the pic to support the tyres that were on my sandcast.

[Steve Swan]

Indeed the decal is from a K0 guard Steve, not from my sandcast.  Sorry if it wasn’t clear.  I’ve amended my post.  I included the pic to support the tyres that were on my sandcast.

gotcha, thanks !