Tank shape r45/65 v r80g/s

[Vulpine2]

I've got an r100r based bike in the final stages of build (not by me, by somebody who knows what they're doing...) and bought an r45/65 tank for it. I've seen these used on similar builds and assumed that it would drop straight on - but apparently the rear underside of this particular tank needed some, uh, 'reshaping' to get it to fit over the frame tubes. I don't know if this was down to the shape of the frame or the tank. I suspect the latter
I now have the option of a rather nice r80g/s tank - but clearly would not want to start bashing that about to get it to fit!
I've always thought the r45/65 tanks were the same as the r80g/s, bar the filler cap and fuel tap arrangements. Can anybody confirm whether they differ underneath? Obviously the best way would be to compare the two types side by side - and that might happen at some point - but I thought I'd start with an enquiry on here.
Cheers, Rob.

 

[scooter paul]

I know for certain that a R100r tank will fit a G/S frame but that in no way answers your question. My guess is the R100r tank is ‘wider’ underneath as the paralever bikes had more electrical gubbins along the top frame tube that need extra room . I’ve nothing in the workshop at the moment to prove or disprove my theory.
Is the tank from the Basic the same as a G/S? Externally it’s the same shape, because the Basic uses a paralever frame.

 

[Grantiii]

 

[Grantiii]

I have just attached 2 pics of tank underside.
The 1st one is of my 86 built R80g/s PD.
The second, belonged to a friend, was painted as a PD... but plainly has more space for electrical gubbins as Scooter Paul Stated.
It is I believe from a Kalahari ... A paralever bike.
Dimensions are written on the yellow tape.
H

 

[mikeyboy]

I've got an r100r based bike in the final stages of build (not by me, by somebody who knows what they're doing...) and bought an r45/65 tank for it. I've seen these used on similar builds and assumed that it would drop straight on - but apparently the rear underside of this particular tank needed some, uh, 'reshaping' to get it to fit over the frame tubes. I don't know if this was down to the shape of the frame or the tank. I suspect the latter
I now have the option of a rather nice r80g/s tank - but clearly would not want to start bashing that about to get it to fit!
I've always thought the r45/65 tanks were the same as the r80g/s, bar the filler cap and fuel tap arrangements. Can anybody confirm whether they differ underneath? Obviously the best way would be to compare the two types side by side - and that might happen at some point - but I thought I'd start with an enquiry on here.
Cheers, Rob.

Hi Rob,
As I said to you yesterday,I suspect the front tank mount is slightly further back than standard due to the frame strengthening gussets.
That mount has been cut off ,stiffener gussets installed then re welded.
I’ll test fit a g/s tank on the bike next week

 

[tofgasp]

The underside of the G/S and R45/65 tanks are perfectly identical. The GS or 100R ones are sligthly different underneath but it fits in one way or the other.
Indeed your tank must have been altered.

 

[Vulpine2]

Hi Rob,
As I said to you yesterday,I suspect the front tank mount is slightly further back than standard due to the frame strengthening gussets.
That mount has been cut off ,stiffener gussets installed then re welded.
I’ll test fit a g/s tank on the bike next week

Doh. That bit of info obviously didn't sink in...
I had a set put on the NZ bike a few months back whilst the bike was stripped down for its' ongoing refurb. Can't remember exact details but pretty sure no removing/rewelding of the tank mount. I wonder if SWT have altered the design recently by splitting that particular gusset into two?

 

[Vulpine2]

The underside of the G/S and R45/65 tanks are perfectly identical. The GS or 100R ones are sligthly different underneath but it fits in one way or the other.
Indeed your tank must have been altered.

Thanks for that, it's what I always assumed. But, as per Mikey's post, it seems the issue may lie elsewhere.