Inch tires versus metric size tires

[Guest]

Hey guys,

I?ve been thinking of replacing my tires and noticed the 3.25-19 and 4.00-18 tires are still offered. I figured these were a thing of the past.. turns out the BMW airhead guys strongly prefer running these tires over a metric equivalent. Some of the guys on the vintage BMW motorcycle forums claim they handle better. I?m wondering if there is any merits to these claims and if it?s worth the extra hassle of acquiring a recent manufacture set.

Matt

 

[hank2]

I had also noticed that there are a couple of bias tires still available in the old inch sizes. Probably only in those particular sizes due to earlier airhead demand. I had rode and wrenched a '72 Beemer airhead for a dozen years. Except for one set of the Conti "twins" ( have forgotten the model numbers) all that I used were metric close equivalents. I wasn't impressed with the handling and certainly not the wear on those particular inch Conti's. They were a vintage style tire though. Michelin and Metzler also had those sizes at one time, maybe they still do. I knw that the old Michelin Macadam 50, maybe obsolete, and the Metzler in the inch sizes were very well liked. They may still be available in your inch size in the front. Metzler and Pirelli were bought out a few years a go by ChemChina.

Other than those vintage style Conti's, I used many sets of Bridgestone S11 Spitfires in 100/90/19 and 110/90/18, which used to be reasonably priced. Also a couple sets of BT45's in those sizes. The S11 front in that size appeared to be noticeably wider than the same size in BT45 ( now BT46). The profile of the S11 front was flatter than the BT45, so maybe that was part of it. BT45 was more edgy, which wasn't always appreciated in the very sensitive early short wheel base model ( 54 in.) I had. Not an issue with the GS's. I looked up your'78 GS750 and was surprised to see the 4.00/90/18 rear speced.

For those that may claim more goodness with the inch tires, I would guess that going a tad too wide on the front with a metric may to be blame. 3.25/90 was closer to a 90/90 or old MM90 size, but a 100/90 is just fine in some brands.

 

[Guest]

Interestingly enough I just had this same conversation with our local guru tyre guy last week about my 450's tyres. I've been running metric sizes (90/90-18 front, 100/90-18 rear) for years with Pirelli Sport Demons and Avon Roadriders.

I'm looking at less expensive alternatives now that it's essentially a commuter only, and when I told him the stock 3.00-18 and 3.50-18 sizes, he said oh, don't go metric, stick with the imperial sizes and go with Metzeler ME22s. Funnily enough they're the same compound as the Sport Demons but half the price! I know which way I'm going when I replace the tyres in the next couple of months

 

[Big T]

I went with the stock sizes in Avon AM 26 for my 1000, I felt it turned sharper than the metric sizes

 

[grcamna2]

I went with the stock sizes in Avon AM 26 for my 1000, I felt it turned sharper than the metric sizes

What is your stock size front tire ?

 

[Guest]

Hmmmm interesting. I also found out the IRC GS-11s that the GS750 and possibly other GS bikes came with are also still available brand new and in imperial sizes. I dunno if I’d go that far for the sake of originality as tire design has come a long way since the mid-late 1970’s.

 

[Big T]

What is your stock size front tire ?

3.25-19. Wire wheels GS 1000