Hi guys

I have read a lot of stuff regarding the following but it still boggles me. I will post the measurements of my bike and I need someone to please clarify a few things for me. The bike in question is a Rockhopper 2010. It has a 80mm suspension fork. The measurements are as follows.
SEAT TUBE LENGTH – CENTER TO TOP 483mm
TOP TUBE LENGTH (HORIZONTAL) 615mm
TOP TUBE LENGTH (ACTUAL) 589.91mm
CHAINSTAY LENGTH 426mm
BOTTOM BRACKET HEIGHT – LOW SETTING 304mm
SEAT TUBE ANGLE (ACTUAL) – LOW SETTING 73°
HEAD TUBE ANGLE – LOW SETTING 70°
WHEEL BASE 1102mm
STANDOVER HEIGHT 806mm
HEAD TUBE HEIGHT 140mm
STACK 599mm
REACH 432mm
GROUND-TOP 907mm

Firstly looking at everything above. If I used a fork with a-c of 465mm on this bike would it make it twitchy or slower steering?

Secondly which I can’t get my head round please bear with me. How do I make this bike more upright rather then racy? Do I use a longer fork with an ac measurement of 465mm above or lower ac if that makes sense?

I’m not looking to buy another bike or anything just trying to get things straight in my head.

I would really like to know the following. I have a bad back. What parts need to be changed to give me a more upright comfortable position? Fork, stem or something else?

I was originally going to get a fork with an a-c of 445mm to compensate for the 80mm suspension fork but I want to make sure I get the right one especially if it makes me a more comfortable bike.

Sorry for rambling on. I don’t really want to get a new bike I would rather if I can do what I can with this bike

An 80mm travel fork for 26″ wheel is about 450mm so a 465mm fork will make it slightly slacker and slower (approx half a degree per 10mm). 445mm fork steeper and faster steering, although probably still higher than with an 80mm travel fork when sag is taken into consideration.

To lift up the front you can add more spacers between the frame and stem if you are changing the forks. Also can change to a higher rise stem, also can change to riser handlebars, also could put in a larger, e.g. fatbike fork/wheel – although this also raises up the BB pushes the seat back etc.

Note: if you lift you the bars a lot then you may need to change cables
Note: lots of things can cause back discomfort, too stretched out, too much weight over front, saddle too high – bike fit can be money well spent.

I think people will soon ask your age weight height and flexibility in order to help you.

oh and type of riding you do and how often.

Thasks for the replies. I understand a bit more now researching the term “slacker” etc.

I measured the crown to axle and it’s 450mm approx. I think from reading if I take into consideration sag etc I would be closer to 440mm or maybe a little less?

465mm maybe overkill am I correct?

I came across adjustable stems that can move the handle bars more up and towards me so that maybe a better option then getting a taller fork.

I’m 5ft11 and about 80 kilos. I’m only 34. Back problem started by not lifting correctly whilst working part time when I was at college. Mostly riding road and a short commute to work. Some off road shortcuts on the way to work.

I have looked into a proper bike fit once I have the fork I want.

All I am trying to achieve is a more upright riding position. I think that sums up by muddled up post before. So the best way to do this would be?

I think a higher-rise bar might be the easiest way to achieve a higher front end without spending a lot or making radical changes (unless there are spacers above your stem which you can move to underneath) – as above, it could be a lot of different factors that are causing you discomfort, you don’t want to go shelling out big money on a new fork only to discover it doesn’t solve the issue.

£20-25 on CRC will find youa set of riser bars to experiment with – the ones below have a 30m rise (of course, if you already have similar or higher rise, this won’t help much)

http://www.chainreactioncycles.com/ie/en/truvativ-stylo-t30-riser-bars/rp-prod67687

Thanks for the information. I have similar handlebars on the bike. The fork needs changing anyway as the suntour crap on there is knackered.

I would really like to know the following. I have a bad back. What parts need to be changed to give me a more upright comfortable position? Fork, stem or something else?

Try moving your saddle backwards if you can, an oft-missed way to reduce pressure on your back and arms by moving your c of g back – raising the bar alone is only part of the solution in this area.
Adding a longer fork will also do this as it’ll reduce the bike’s angles (rotate the bike up and back around the rear axle).

Thanks for all the help guys.