91 Kona Cindercone fork needed!

[RetroSteve]

Hi,
I picked up a 91 Kona cindercone at the local market for £25. It's a strange mix of well looked after and not so well looked after - regreased fork steerer in the head tube and totally knackered forks and sticky, never been degreased shifters.
Now it's mostly original parts in pretty good condition, only the fork is an rst 461 and fully compressed cos its got now spring or oil or whatever the hell it's supposed to have, so I need a new fork - I'm thinking rigid.
Can anyone tell me what length fork will maintain the geometry. From a bit of googling it looks like 450mm but I can't find any forks that are that long. The closest I can find is the surly instigator at 448mm - is that a good choice?
Cheers
Steve

 

[Anthony]

I like that colour I must say. £25 is not a bad price at all.

The RST is an elastomer fork from around 97 or so, and it looks as though the elastomers have crumbled away to nothing as the fork is way shorter than it should be. I doubt whether there would be much point in trying to revive it to be honest, as elastomers aren't available and it wasn't much good in the first place.

The frame is designed for a 39cm fork, measured from the axle centre to where the crown race sits. That was the length they used up until 1993, and you will see a Project 2 for sale from time to time from that era. The exact one for 1991 is black as shown below. I think your bike is a size 18, i.e. 18.75" seat tube c-t and does it have a 13cm head tube? If so, you would need a 16cm threaded steerer.

On the other hand, if you want to stick with that aheadset and ahead stem, you will need an ahead steerer of 20cm absolute minimum. I think your best bet/only option for an ahead fork with a 39cm a-c would be a Pace RC30/31 where you can replace the steerer.

The alternative is to use a later Project 2 of 41cm a-c, which will give slightly less sharp steering, but not the end of the world and some people actually prefer it. P2s were ahead from 1997 onwards and they were black from 1998 onwards, but the triple-butted ones are best and you're more likely to find a triple-butted 97 than a later year. 97 were gunmetal grey.

I'm sorry if all that complicates the issue, but that's about it really.

 

[Anthony]

Just look at this beauty!
http://cgi.ebay.co.uk/ws/eBayISAPI.dll? ... :MESELX:IT

 

[RetroSteve]

Hi - you are right about the elastomers.
I'll check the frame size and confirm it...

Oh no, I'm really confused about the forks now....;-)

I think I want to buy a new fork and keep the current ahead set. so would this be ok?
http://www.winstanleysbikes.co.uk/product/5454/Gusset_Jury_SL_Fork
it's 13mm over the 39cm that you've said is the right length.
Excuse my ignorance but this is my first 'project' - will increasing this length change the head angle? bottom bracket etc. and what's the limit and why does that matter?
39cm seems very short compared to the rigid forks I've seen available on' tinternet...

 

[cce]

that fork would be ok for length, but it's a full 400g heavier than a triple butted P2

 

[Aaldert]

P2

Hi,

Maybe I can help with the measurements.
I have a 1996 18" Cinder Cone with a threaded matte gunmetal gray tripple butted P2 and a 1997 16" Hahanna with an ahead shiny gunmetal gray "normal" P2.

On the picture below the Hahanna's fork is mounted on my 1997 16" Cinder Cone (blue one).

 

[Anthony]

I think I want to buy a new fork and keep the current ahead set. so would this be ok?
http://www.winstanleysbikes.co.uk/product/5454/Gusset_Jury_SL_Fork
it's 13mm over the 39cm that you've said is the right length. Excuse my ignorance but this is my first 'project' - will increasing this length change the head angle? bottom bracket etc. and what's the limit and why does that matter? 39cm seems very short compared to the rigid forks I've seen available on' tinternet...

It depends what you want to do with the bike. As it says, the Gusset is a trials fork basically, which explains why it's so heavy. I would guess it would be pretty uncomfortable as an xc fork, and it isn't just comfort either - when a fork is as stiff as that it slows you down. You need a bit of compliance to help the tyre to grip.

The reason why most modern rigid forks are so much longer is that they're for frames that were designed for suspension - a 100mm fork is c47.5cm long, or c45cm with sag. So a frame designed for a 100mm fork would need a rigid of around the same length. The 91 Cinder Cone is pre-suspension and is designed for a 39cm fork, as in the picture I posted.

Yes, fitting a 40.3cm fork would affect the geometry and bb height, but not by much as I said above. And if you're going to stick with that short stem, you've already got quicker steering, so a slightly longer fork (which slows the steering) will just counterbalance that.

I still think your best bet if you want to use the bike for xc or commuting is a 41cm Project 2 from 97 onwards, preferably triple-butted. You can still get them new, but if you're patient you'll find a suitable one on eBay in days/weeks rather than months. £25-30 for tb, £20-25 for plain-gauge. PM me if you see something and you're not sure if it's right.

 

[Anthony]

Re: P2

Hi,
Maybe I can help with the measurements.
I have a 1996 18" Cinder Cone with a threaded matte gunmetal gray tripple butted P2 and a 1997 16" Hahanna with an ahead shiny gunmetal gray "normal" P2.
On the picture below the Hahanna's fork is mounted on my 1997 16" Cinder Cone (blue one).

Nice bikes there. The blue one is in fact a size 18 and the gold one is a size 19, although they changed the shape/geometry so your 1996 size 19 has a 13cm head tube, which is the same length as on RetroSteve's 1991 size 18.

Nice subtle brake booster you went for!

 

[Aaldert]

Hi Anthony,

Since when changed Kona the geometry? I am curious.
Is it because of the suspension forks?
I know that the modern bikes have different geometry than the older ones because of the longer travel forks.

I measured the bikes and held the measurements to the 1997 catalogue, so I am pretty sure y bikes are a 18" and a 16".
http://www.konaretro.com/articles/catalogues/1997/97Page29.jpg

If I understood you correct, my 1996 18" bike has roughly the same size as a 1991 19"?

 

[Anthony]

Yes they did change the geometry to suit suspension better.

From 1994, the P2 was increased in length from 39cm to 41cm, but the bar heights were kept the same by reducing the length of the head tubes by 2cm. So a 1991 size 18 had a 39cm P2 and a 13cm head tube, and a 1997 size 18 had a 41cm P2 and an 11cm head tube, total 52cm in each case.

From 1994, it was size 19 that had a 13cm head tube (16=9cm ht, 17=11cm ht).

In addition, from 1993 they measured size from centre of bb to top of seat tube (c-t basis), whereas the size of RetroSteve's 1991 frame is measured from the outside of the bb shell - i.e., it is the length of the seat tube itself that is 18" on his bike (giving a c-t of 18.75).

However it's the top tube length that is the most important measure. I don't find the horizontal measure that Kona quote there very helpful, but measured along the tube and c-c, 94on top tubes are 19=575mm, 18=562mm, 17=550mm, 16=538mm. I believe that RetroSteve's 1991 size 18 has a c-c tt of 560mm, i.e., very similar to a 1994 size 18.