1

So recently whenever I am riding my bike and I push down to a certain point, my bike makes a grinding noise and I can feel the main frame grinding as well, I can't seem to identify where it is coming from, and why my bike is making that sound. The model of the bike is a Kona Stinky Deluxe 2008.


Stock Photo
Stock Photo of this model

4
  • 1
    With “push down”: Do you mean compressing the suspension? So it occurs independent of pedaling and is therefore not related to the drivetrain?
    – Michael
    Feb 24, 2022 at 6:12
  • 1
    What kind of brakes do you have? Is this a mountain bike or road bike or what is it? Feb 24, 2022 at 9:50
  • 1
    Is it when you push down on the pedal when riding? If so, is it only one pedal or both?
    – FreeMan
    Feb 24, 2022 at 14:13
  • I compress to a certain point and it starts grinding yes, I am not pedaling or braking, just compressing the suspension
    – Keyin Liu
    Feb 24, 2022 at 23:48

2 Answers 2

4

If this grinding noise only happens when the rear suspension is compressed\actuating, my first step would be to check the pivot points of the rear triangle\suspension.

Dirt may have accumulated between the pivot points. A penetrating oil could help with this, or if you're feeling adventurous, disassembling the pivot points for a cleaning and re-lubing. This also applies to the pivot points of the spring coil, and the coil itself. The "dial" that tensions the coil could be loose and developed play under pressure, and\or debris has gotten between it and the plate as well.

More than likely, as has been mentioned previous, something is coming into contact with the rear tire as the rear triangle compresses under load. I'd first check if any housing lines (brake line, gear line) are close to the tire. Under compression, the tire can move closer to these lines, and rub. Especially with any frame flex. Another common cause of this could be if the rear wheel was removed at some point, then not reinstalled in proper alignment. It could be off to one side by a few millimeters. Keeping in-line with this thought process, if you installed new tires recently, of a larger width, they may be maxing frame-tire clearance. Just clearing enough to spin normally, but under flex\compression, creating rub. Another potential cause of this could be if you have a broken wheel axel. It'll operate mostly normal, expect under extra load, like the rear suspension compressing, for instance, creating rub.

Loose spokes, can also cause a rub issue, where under pressure the rim actually bends enough to cause contact for the tire on frame.

3

Based on info within your question and the clarifying comment you made, I'm thinking that the grinding noise may be tire rub on the frame or cabling when the suspension sags to a certain point. The tire rub could even be taking place on a seat or chain stay when a combination of suspension and frame flex change the already tight tire clearances in these areas. The rolling tire then contacts a frame aspect and that sensation can be described as "grinding." Even just the outer edge of a rolling tire's knobbies can brush along an aspect of the frame. The successive contact of a series of knobbies would yield a grinding sensation and/or noise. For instance, my old full-suspension MTB is equipped with knobby tires that are at the upper size limit as far as width for this particular frame. Sometimes I'll sense the tire rub--or on close examination can see that the tire clearance at the chainstays is not balanced. A gap of 5mm is seen between tire and the left chainstay, whereas on the right, the gap is 1mm. There's enough irregularity in the tire's width, or the rim has become untrue in an area, and because of that and the too narrow of clearance on the right, some of the knobbies will tick the frame on the way by. In my case there are 3 root causes I've found that will mess up the tire clearance and lead to rub. The first I mentioned above being the run-out of an rim out of true. Usually that's not so severe that it would cause rub on the frame (typically an wheel out of true won't cause frame rub. Contact with rim brakes, yes, but not the frame), but because of the nearly too-wide tires with narrow clearance, a run out can be enough for the outer knobs to rub. The second cause is the rear wheel becoming uncentered in the dropouts. The hub has a 10mm axle with 5mm QR skewer and after a period of rough riding and time the wheel will shift in the dropouts-- just takes a couple millimeters of movement on one side of the hub seated in the dropouts to cause enough misalignment if the whole wheel to disrupt the clearance and tire rub. The third cause is the rear triangle becoming slightly off center because of a linkage bolt that has loosened itself. The excess play at that connection as well as the imbalance of torque in the system of linkages leads to lateral movement of the rear triangle upsetting the delicate balance that gives me adequate tire clearance with my set up.

Thus, I suggest you and a friend ride along to see if you can determine where the sound or sensation is coming from. You can each take a turn riding the problem bike while the other observes to at least get a specific location. Off the bike you can examine the bike paying particular attention to frame spacing, presence of rub marks or absent paint on the interior aspects of the seat and chainstays as well as the back side of the bottom bracket shell. You can remove the rear wheel and replace it back in the dropouts making sure it's fully seated in the dropouts and centered in the frame. Examine the linkages noting the presence of any lateral play. Use a torque wrench on each linkage bolt and get them to proper torque per the maker's specs. Check the amount of sag your rear suspension has when you're sitting on the bike in a riding position. There are many, many articles and how to videos dealing with sag and it's measurement. You typically want to have 25-30% of your rear shock's stroke length taken up by the sag of your riding weight. If it's more than this, the spring rate is too soft, the bike is riding too low in it's travel and this can cause some structures to come into contact during suspension activation. If you're easily and/or frequently bottoming out the suspension on rides, thats an indication you're spring rate is too soft. Related to suspension, this time at the front, make sure your suspension fork is appropriate for the bike. This means that it is the correct wheel size (you're running a 26" inch fork, with a 26" tire that's not too wide for the fork), and the travel of the fork is within spec of the bike. An '08 Kona Stinky Deluxe is a 26" wheeled, full suspension MTB spec'd with a 180mm travel Marzocchi fork, and a Marzocchi rear shock yielding 175mm travel. Any current suspension should closely match those. The max tire width is listed as 2.5" so check that your tires are within spec.

Overall it can be tough to even locate exactly where a noise is coming from on a bicycle. An extra pair of eyes and ears from an observation perspective can help immensely. So too can an overall inspection of the bike for signs of imbalance or excess wear which can direct your observation efforts and lead to insight as to the source and cause of the grinding.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.